Modern Concept Science and Technology 10 New

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 297 or, n2 = 2000 × 11 220 = 100 Therefore, the number of turns in the secondary coil must be 100. Solved Numerical 11.2 In a transformer, the ratio of secondary turns to primary turns is 4:3. Which type of transformer is it? Find the secondary voltage when the transformer is connected to a power supply of 220 V. Solution: Given, The ratio of secondary turns to primary turns (n2 : n1 ) = 4:3 This transformer has more turns in secondary coil. So, it is a step-up transformer. Primary voltage (V1 ) = 220 V Secondary voltage (V2 ) = ? According to the transformer formula, V2 V1 = 4 3 or, V2 220 = 4 3 or, V2 = 220 × 4 3 = 293.33 V Therefore, the secondary voltage is 293.33 V. Solved Numerical 11.3 The coil of a transformer has primary turns double of secondary turns. Calculate the input voltage if 220V is generated by the secondary coil. Solution: Given, Let, the number of turns in secondary coil (n2 ) be x Then number of turns in primary coil (n1 ) is 2x Input voltage (V1 ) = ? Output voltage (V2 ) = 220V According to the transformer formula, V2 V1 = n2 n1 or, V1 n2 = V2 n1 or, V1 × x = 220 × 2x or, V1 = 440 The input voltage (V1 ) = 440V.

298 electRicity and magnetiSm Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur HOT SKILL HIGHER ORDER THINKING SKILL 1. When we wrap a matchbox by an insulated copper wire connected to the galvanometer and drop a bar magnet, north pole down, Will there be a deflection in the galvanometer? What is its cause? What would happen if the magnet is dropped, south face down? Which principle is being tested here? If we wrap a matchbox with an insulated copper wire connected to the galvanometer and drop a bar magnet, north pole down, then it will certainly deflect. The cause of deflection is the flowing of induced current through the galvanometer due to changes in magnetic flux when a bar magnet passed through the coil of a conductor. If the magnet is dropped, south face down in the same coil, the needle will deflect in opposite direction. Faraday’s laws of electromagnetic induction are being tested in this experiment. 2. How does the topography of Nepal support the production of hydroelectricity? The topography of Nepal is very suitable for the production of hydroelectricity. Its altitude ranges from 60 meters to 8848 meters. Nepal is a slanted surface that faces south. So, there is enough sunshine to melt snow from the mountains. This water runs down the mountains to produce many rivers throughout the country. All of the rivers flow faster because Nepal is a slanted surface. If we can successfully make water dams, we can collect a huge quantity of water. We can drain the dam through the tunnel downhill. The kinetic energy of the water can rotate the turbine to produce a tremendous amount of electricity. 3. Differentiate between a transformer and an electric motor. The differences between transformer and electric motors are: SN Transformer SN Electric motor 1 A transformer is designed to change the voltage of AC. 1 An electric motor is designed to change electricity into kinetic energy. 2 It cannot work with DC. 2 An electric motor can work with DC. 4. Alternating current generated in hydropower stations is transferred to sub-power stations at a very high voltage. Sub-power stations send electricity at 230 voltages for domestic use. However mobile devices, torch lights, laptops and many other devices run at lower voltages. Which device helps to alter the voltage of AC? Would AC be useful for us without this device? Why? How does this device help us to consume AC for domestic purposes? Alternating currents generated in hydropower stations are transferred to sub-power stations at a very high voltage. The sub-power stations send them at 230 voltages. However mobile devices, laptops etc run at lower voltages. The device that can change the voltage of AC is a transformer. AC would not be useful without a transformer because AC is sent at a higher voltage from hydropower stations. Many domestic electrical devices run only at a lower voltage. Only the transformer can change the voltage of the AC for electronic devices. Transformer help to consume AC in the following way The voltage of AC is made very high by a step-up transformer to transfer it from the hydropower station to the sub-power station so that the current would not be wasted. Then the step-down transformer is used at the sub-power station to lower its voltage to 230 Volts. The AC supplied for domestic purposes is 230 volts. Adapters and chargers contain step-down transformers that lower the voltage down to the required magnitude. Hence AC can be consumed because of the transformer.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 299 5. When electricity from the solar panel is directly supplied to the fridge, it won’t work. A fridge usually runs on AC. So, when electricity from the solar panel is directly supplied to the fridge, it won’t work because solar panels produce direct current. 6. Who discovered the magnetic effect of electricity? If a current flowing in a conductor can produce a magnetic field around it, can a conductor placed in a magnetic field produce current? Under what condition is it possible for a conductor placed in a magnetic field to produce electricity? What happens if we supplied current in that conductor instead? What is this phenomenon called? Hans Christian Oersted discovered the magnetic effect of electricity. A current flowing in a conductor can indeed produce a magnetic field around it but a conductor placed in a magnetic field cannot produce electricity when it is at rest. However, if the conductor is in motion inside a magnetic field, a current will be induced. If we supply sufficient current in that conductor placed in a magnetic field, it will produce motion. This phenomenon is called the motor effect. 7. Study the given diagram and answer the following questions. i. Name the device. The device shown in the above diagram is an electric motor. ii. What is the reason for the production of motion in the conductor? The conductor is inside a magnetic field. When current is passed in the conductor, another magnetic field is produced. Two magnetic fields repel each other and produce motion. iii. What is the name of the phenomenon that produces motion in the conductor of that device? The phenomenon that produces motion in the conductor of that device is called the motor effect. iv. What can be done to increase the rate of rotation? We can supply a higher voltage of electricity to increase the rate of rotation or use a powerful magnetic field. v. Which rule helps to find the direction of rotation of a conductor placed in a magnetic field? Fleming's left-hand rule helps to find the direction of rotation of a conductor placed in a magnetic field 8. Chargers of laptops and mobile phones have transformers in them. Mention the type of transformer they possess. Why do they have that transformer? The chargers of laptops and mobile phones have a step-down transformer in them. They have a transformer in them to lower down the AC voltage from 230 Volts to the required voltage. These devices do not operate at a higher voltage. 9. Ashmita uses bicycles to go to school. She has installed a dynamo on her bicycle so that she can ride the bicycle at evening. She was late for home so she pedalled faster. She noticed that the faster she rode the bicycle the brighter the bulb glowed. She wants to know why the bulb glowed brighter when she rode a bicycle faster. Explain it to her in simple words.

300 electRicity and magnetiSm Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur As informed Ashmita pedalled faster to increase the velocity of the bicycle and noticed that the bulb glowed brighter. The cause for this is faradays laws of electromagnetic induction. According to the faradays second law of electromagnetic induction, the magnitude of induced emf is equal to the rate of change of magnetic flux. It means if there is more change in magnetic flux, more emf is produced in the conductor. Dynamo is based on electromagnetic induction. So, when she pedalled faster, the permanent magnet of the dynamo also rotated faster. Since the magnet is rotating inside the coil, the rate of change of magnetic flux also increased. As a result, higher emf was produced and the bulb glowed brighter. 3 STEPS 3 STEPS EXERCISE EXERCISE STEP1 1. Select the best answers from the given alternatives a. What is a conducting path in which current can flow? i. conductor ii. conducting path iii. electric circuit iv. electric current b. What kind of electricity has zero frequency? i. direct current ii. alternating current ii. induced current v. lightning c. In what direction does the free north pole move from outside the magnet? i. east to the west ii. south to the north iii. north to the south iv. toward the centre of the earth d. What is the name of the device shown below? i. generator ii. dynamo iii. motor iv. electric turbine e. Why does bicycle dynamo glow brighter if the bicycle runs faster? i. higher change in magnetic flux ii. slower change in magnetic flux iii. no change in magnetic flux iv. magnet grows powerful if the bicycle runs faster f. Which one of the following produces the current that has frequency? i. solar panel ii. simple cell iii. dry cell iv. bicycle dynamo 2. Define the following terms with required examples. a. Current b. Direct current c. Kilowatt hour meter d. Hydro energy d. Thermal energy f. Wind energy g. Electromagnetic induction h. Generator

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 301 i. Electric motor j. Solenoid k. Alternating current l. Bicycle dynamo m. Motor effect n. Transformer o. Step-down transformer p. Step-up transformer q. Mutual induction r. Magnetic flux 3. Answer the following questions in very short. a. Write the full form of CFL and MCB. b. What is the commercial unit of electricity? c. Write down the average value of current and frequency in Nepal. d. In which principle, generator and dynamo are based? What type of current is induced by dynamo? e. Write down Faraday's laws of electromagnetic induction. f. What is a generator? Write its principle. g. Write down the principle of the transformer. h. What is the direction of the magnetic field if a current flows upward in a straight conductor? i. Which type of transformer is used in the hydropower station and sub-hydropower station? STEP2 4. Give reasons: a. Kinetic energy is produced on an electric motor when we pass electricity in the conductor which is placed inside a magnetic field. b. A stationary magnet does not induce a current in a coil. c. Needle of a magnetic compass kept near a straight current-carrying conductor deflects. d. The brightness of the bicycle dynamo bulb increases when the speed of the bicycle increases. e. Thermal power plants should be discouraged. f. Core of a transformer is laminated. g. The number of turns in the primary and secondary coils of a transformer is never made equal in number. h. A transformer does not alter the voltage of direct current (DC). i. A transformer cannot change the emf of the dry cell. 5. Differentiate between the following. i. Alternating current and direct current ii. Electric motor and generator iii. Step-up transformer and step-down transformer iv. Dynamo and generator

302 electRicity and magnetiSm Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 6. Answer the following questions in short. a. 'Frequency of the power supply in the domestic circuit is '50 Hz'. Write its meaning. b. Draw the current-time graph for AC and DC. b. What is meant by the magnetic effect of current? Write its applications. c. What are the factors on which the strength of the induced current depends? d. What change occurs in the brightness of the bulb connected to the bicycle dynamo when the speed of rotation of its wheel increases? e. Write in short about the methods to increase the magnitude of the induced current from a bicycle dynamo. f. Enlist Faraday’s law of electromagnetic induction. f. How can we increase the strength of an electromagnet? f. 'Use of alternating current would be limited in absence of transformer'. Justify this statement. g. Write the two laws on which a transformer is based. h. What is a step-up transformer? Write its two applications. i. What is a step-down transformer? Write its two applications. j. How is a large amount of electricity generated by using a generator? Explain in short. k. Explain in short about the construction of a transformer and its working mechanism. l. Explain in short about the construction and working mechanism of a bicycle dynamo. m. Write the functions of the step-up transformer and step-down transformer. n. Describe the structure of AC generator. STEP3 7. Answer the following long questions. a. Describe Fleming's right-hand rule with the help of a diagram. b. Demonstrate the magnetic field around the straight current-carrying conductor by an activity. c. In the given figure, a copper wire is being moved perpendicularly to the magnetic lines of force in the U-shaped magnet. Two ends of a wire are connected in Galvanometer. i. Why does the Galvanometer show deflection when the wire is moved up and down? ii. Suggest two ways that can increase the deflection of the galvanometer.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 303 d. Study the given diagram and answer the following questions: i. What type of transformer is shown in the figure? Give reasons. ii. Calculate the output voltage. [Ans: 45 V] iii. Give one use of such a transformer. e. Draw the diagram of a step-up transformer and a step-down transformer. f. Draw the diagram to show the magnetic field around a solenoid and a straight conductor. h. What is the direction of the magnetic field around the solenoid? Explain with the help of Maxwell'sright-hand grip rule. i. Study the given diagram and answer the following question. i. What happens in the needle of the galvanometer when the magnet is pushed inside the coil? ii. What happens if the bar magnet is repeatedly pushed in and out of the solenoid at a greater velocity? iii. What happens to the deflection of the needle when the magnet is at rest? 8. Numerical a. The pd of the power supply to the primary coil of a transformer is 220 V and the turns in the primary coil are 2000. What must be the number of turns in the secondary coil to run a radio of 11 V from the transformer? [Ans: 100 turns] b. A transformer has 600 turns in the primary coil and 1200 turns in the secondary coil. The potential difference across the primary coil is 110 V. What is the potential difference induced across the secondary coil? [Ans: 220 V] c. The power supply is 240V and the number of turns in the primary coil of a transformer is 1000. What should be the turns in the secondary coil to generate an output of 12V, 24V and 120V? [Ans: 50, 100, 500 turns] d. The number of turns in the primary coil of a certain transformer is 440 times more than that in the secondary coil. Calculate the input voltage in the primary coil if the e.m.f. generated in the secondary coil is 220 V. [ Ans: 9680 V] e. In a transformer, the secondary turns are 4 times more than the primary turns. What should be the input voltage in the transformer to obtain an output of 220 V? [Ans: 55 turns] f. In a transformer, the ratio of the secondary turns to primary turns is 2:3. Which type of transformer is it? Find the secondary voltage when the transformer is connected to a power supply of 220 V. [Ans: step down, 146.667 V] 1000V 450 turns Output=? 100 turns

304 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Key terms and terminologies of the unit 1. Universe : The universe is all of space and time and their contents such as matter and energy. 2. Gravitation : The force of attraction between any two objects having mass is called gravitation. 3. Nebula : The nebula is a cloud of hydrogen or helium gases in space. 4. Galaxy : A galaxy is a group of billions of stars. 5. Black holes : Black holes are the remains of massive dead stars with infinite density and gravity. 6. Observable universe : The visible part of the universe from the earth is called the observable universe. 7. Big bang theory : The theory that describes how the universe expanded from an initial state of high density and temperature is called the big bang theory. 8. Close universe : The universe in which the masses in the universe can produce gravitation that exceeds the expanding forces. As a result the expansion ceases, reverses and collapses into a point where space and time do not exist anymore is called the close universe. 9. Big crunch : The hypothesis in which every single matter comes close and condenses into an infinitely dense and hot singularity if the gravitation is far greater than expansion force is called big crunch. Sequence of Curriculum Issued by CDC  Importance of gravitation in the universe (existence of satellites, planets, stars, and galaxies in space)  Origin of the universe based on the big bang  Conclusion of Hubble’s observation of the motion of the heavenly objects  Possible fate of the universe, based on gravitation (open universe, close universe and flat universe) UNIT Universe 12 Estimated teaching periods Theory Practical 4 1 Georges Lemaitre is well known for the Big Bang theory. He was born in Belgium on 17th July 1894 and died on 20th June 1966. He was a cosmologist, astrophysicist and mathematician. He was the first to realize that the universe is expanding which was later confirmed by Edwin Hubble (November 20,1889 -September 28, 1953), an American astronomer. He first derived Hubble’s law and Hubble constant which is now called Hubble-Lemaitre law. He proposed the Big Bang theory of the origin of the universe. Georges Lemaitre About the Scientist

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 305 10. Open universe : The universe in which the masses in the universe cannot produce gravitation to slow down the expansion of the universe. As a result the expansion continues until all heavenly objects are alone is called open universe. 11. Big chill or big freeze : The hypothesis in which every single matter moves infinitely far away from each other and every form of energy is uniformly distributed already is called big freeze. 12. Flat universe : The universe in which gravitation can slow down the expansion from big bang. But in an infinitely long time the formation of stars and galaxies is possible is called flat universe. Introduction The word universe is made up of two words: ‘uni’ meaning one and ‘versus’ meaning turned into. The vast surrounding space which consists of everything seen or unseen including all planets, satellites, stars, galaxies, constellations, comets, dust particles, matter, energy, etc. is called the universe. Universe is a huge secret. It is because the most fundamental questions like the shape, size, origin and expansion are not fully understood by science. The branch of science that studies the universe is called Astronomy. The branch of physics that studies the physical nature, laws and principles of astronomical objects and phenomena in the universe is called Astrophysics. Scientists estimate about 1022 stars in the universe. The universe exists because of gravitation. The force of attraction between any two objects having mass is called gravitation. It was discovered by Sir Isaac Newton. The gravitation is a pulling force. It has various effects on the universe. Importance of gravitation in the universe i. Formation of star The nebula is a cloud of hydrogen gases in space. The gravitational pull condenses them into a huge ball of gas. It compresses due to its own gravity and finally gains sufficient pressure and temperature to start a thermonuclear fusion reaction. Finally, it forms a star. ii. Formation of the solar system When the star (sun) is formed its gravitation pulls the nearby heavenly objects to form the solar system. Planets, millions of asteroids, comets, dwarf planets, etc. revolve around the sun in response to its gravity. The gravity of the planets capture satellites. Satellites revolve around the planets. Moon is a natural satellite of the earth. Fig: nebula Fig: solar system

306 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur iii. Formation of the galaxy The gravitational pull among the stars brings them closer to form a galaxy. A galaxy is a group of billions of stars. Some galaxy have black holes in their nucleus. Black holes are the remains of massive dead stars. They possess infinitely large gravity and density. The gravitational pull coming out from the black holes are observed throughout the galaxy and beyond the galaxy. The gravitational force of the galaxy pulls hundreds of billions of stars and make a gigantic galaxy. We live in a spiral galaxy called the Milky Way galaxy. It is a group of at least 100 to 400 billion stars. A galaxy is a collection of countless stars. The diameter of our home galaxy is about one lakh light years. This galaxy is formed because of the gravitation among the black hole Sagittarius A. As a result, billions of stars are being pulled toward it. iv. Formation of atmosphere around the earth The air is a matter. It has mass. So, it is attracted by the gravity of the earth. Earth’s gravity gives weight to the air. Air is pulled down towards the earth. So, it cannot escape from the earth. The layer of air around the earth is called the atmosphere. It exists due to the gravity of the earth. FACTS WITH REASONS The moon revolves around the earth. The moon revolves around the earth because the gravitational force exerted by the earth on the moon provides the necessary centripetal force for the moon to revolve around the earth. Billions of stars are present in a galaxy. The gravitational pull among the stars brings them closer to form a galaxy. So, gravitational force is a factor due to which billions of stars are present in a galaxy. Why does solar system exist? When the star (sun) is formed its gravitation pulled the nearby heavenly objects to form the solar system. Planets, millions of asteroids, comets, dwarf planets, etc. revolve around the sun in response to its gravity. ACTIVITY 1 Does gravitation affect our daily life? Make a list of various daily activities that is possible because of gravitation. Fig: milky way galaxy Gravity is the weakest force in the universe. Even lifting a book is work against gravity. MEMORY TIPS Fig: atmosphere around the earth

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 307 Big bang theory As observed through Hubble’s telescope it appears that the universe is expanding as if it is an outcome of a huge explosion. Then, based upon this observation a theory on the origin of the universe is made. This theory is popularly known as the big bang theory. The theory that describes how the universe expanded from an initial atom of high density, high energy and temperature is called big bang theory. Many variations about the big bang are available. Georges Lemaitre first suggested the big bang theory in 1920s. The Big Bang theory is the leading explanation of how the universe began. George Lemaitre imagined that the universe began from a single high energy, high temperature, high pressure and high density atom. It suddenly exploded and expanded 13.8 billion years ago. Finally, the explosion magnified to form the current universe. According to the big bang theory, the big bang produced space and time where energy could stay. Before big bang, the four fundamental forces i.e., gravitational force, electrostatic force, strong nuclear force and weak nuclear force were together in an atom. In this situation, the universe was in the highly condensed state of an atom. Due to high pressure and high energy, the atom exploded(big bang) producing universe. As a result of this big bang, all the heavenly bodies like stars, planets, comets, asteroids, meteors, etc. were formed. Due to the mass of these heavenly bodies in the universe, there is force of attraction called gravitational force. It is attractive force. It is also called centripetal force. This force tries to bind the heavenly bodies together. Similarly due to the big bang force, the heavenly bodies try to move far away from each other. This is because it is a centrifugal force. FACTS WITH REASONS Why were there no stars at the beginning of the universe? There were no stars at the beginning of the universe because it took millions of years for hydrogen gases to accumulate into a nebula which could give birth to stars. ACTIVITY 2 Make a concept map to explain the origin of the universe from the big bang up to the current form of the universe on a chart paper and paste it in the class. Conclusion of Hubble’s observation Hubble’s telescope is a very large telescope launched into space on April 24, 1990. It is used to take sharp photos of space, planets, stars and galaxies. It has made lots of discoveries such as the age of the universe, black holes, the relation between redshift and the distance of galaxies from earth etc. Based on more than one million observations made by Hubble, it is observed that the universe is expanding as well as accelerating. The big bang means the explosion. So, Fig: big bang

308 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur naturally, things should be moving away from the centre of the explosion. The Hubble’s telescope helped to find evidence to support the big bang theory. From the Hubble's observation, it is concluded that the galaxies are expanding as well as accelerating. The heavenly bodies which are seen smaller are also very far from the earth. They have more velocity. He plotted a graph between velocity of the heavenly bodies and distance between them. He gave an equation v = Hd to calculate velocity of the galaxies as well as distance between them. This is called Hubble's law. In this equation, 'v' is velocity of galaxy, 'd' is distance between the heavenly bodies and 'H' is the Hubble's constant. Its value is 73 km/s/ Mpc (kiloketer per second per Mega parsec). This equation also shows that if there is one mega parsec distance between two galaxies than they are moving apart by 73 km/s velocity. If the distance between two galaxies is expressed in mega parsec and multiplied by Hubble's constant than we get the velocity by which heavenly bodies are moving apart. From the Hubble's study it is also clear that those galaxies that are farther away from the earth are moving away faster than those galaxies which are closer to the earth. It is also called Hubble’s law. Since the universe is expanding, light from some galaxies can never reach us because they have travelled very far from us already. Only some portion of the universe is visible to us. This visible part of the universe from the earth is called the observable universe. FACTS WITH REASONS Why do many scientists agree that the universe is expanding? Many scientists agree that the universe is expanding because they have observed that the spectral lines from distant galaxies shifts toward the red line of the spectrum which means the source of light is moving away from us. ACTIVITY 3 Observe these two pictures taken from Hubble’s telescope. Compare it with the pictures taken from the James Webb telescope. Why are the distant galaxies redder in the picture? Fig: the pictures of space taken from Hubble’s telescope Fig: the same pictures of space but taken from James Webb telescope. Fig: the relation between velocity and distance in Hubble's study

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 309 ACTIVITY 4 Why do many scientists agree that the universe is expanding? Taking the help of internet make a report and present in the class. The fate of the universe As observed by Hubble’s telescope, we know that the universe is expanding. Will it expand forever or will it stop expanding and condense back? What will happen to the universe at last? These are various queries that come to mind. Many scientists have put forward many different theories about the fate of the universe. The most reasonable hypotheses are the close universe, open universe and flat universe. These models of the universe are based on the magnitude of gravitation, energy from the big bang and critical density. The gravitational force pulls heavenly objects closer (centripetal force) whereas the energy from the big bang and the pushing force from dark energy pushes heavenly objects away from each other (centrifugal force). Density of the universe The ratio of the total amount of matter present in the universe to the volume of the universe is called the density of the universe. The net centripetal force produced by gravitation depends upon the average density of the universe. And the balance between a centripetal force from gravitation and a centrifugal force from the big bang determines the future of the universe. The condition in which the centripetal force from gravitation balances the centrifugal force from the big bang just right, the galaxies which are accelerating right now will slowly but surely slow down. As a result, they come to rest somewhere in the distant future. The mean density of the universe which can produce the above situation is called critical density. If mean density of universe is greater than critical density, then gravitational force will be stronger than the pushing forces then the universe will be positively curved closed surface like a sphere and gives birth to a closed universe. If mean density of universe is lesser than critical density, gravitational force will be weaker than the pushing forces then the universe will be a negatively curved surface like a hyperbola giving birth to an open universe. If the mean density of universe is equal to critical density, gravitation will be equal to the pushing forces, then the universe will be flat with no curve and gives birth to the flat universe. Close universe Let’s suppose the universe is expanding as observed by Hubble’s telescope. However, we have observed that the gravitational forces of the black holes are powerful enough to drag billions of stars to form galaxies. Those stars are locked within the gravitational fields of the black holes and do not escape. What if the mean density of universe is greater than critical density and there are sufficient masses in the universe that can produce a tremendous 1. The ratio of total mass of the universe to the total volume is called mean density of the universe. 2. The value of mean density of the universe which can protect the expanding velocity of the heavenly bodies is called critical density. MEMORY TIPS The closed universe is spherical or elliptical. MEMORY TIPS

310 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur magnitude of gravity to actually counter the acceleration produced by the big bang and the dark energy? Then the acceleration of the expanding universe must decrease and reach zero provided enough time. Then the gravitational force will reverse the big bang. Every matter that has moved away from the centre of the universe will start to return back. All of the materials will be combined similar to the initial state before the big bang. Such a scenario is termed a big crunch. The hypothesis in which every single matter comes close and condenses into an infinitely dense and hot single body if the gravitation is far greater than expansion force is called big crunch. Many scientists assume that the universe is oscillating (Big bounce). It means the big crunch and big bang occur alternately. Therefore, the universe is said to be the close universe in case the masses in the universe can produce gravitational force that exceeds the expanding forces due to big bang so that the expansion ceases, reverses and collapses into a point where space and time do not exist anymore. FACTS WITH REASONS The closed universe is formed if gravitation is more than expanding forces. If gravitation is more than expanding forces, the expansion will slow down. Then the universe will curl into the ball. It gives birth to a spherical close universe. ACTIVITY 5 Discuss the idea of a closed universe with your friends and teacher. Open universe Let’s suppose the universe is expanding as observed by Hubble’s telescope. It is also observed that the things farther away from us are accelerating faster. It might be because the pushing force from the energy of the big bang and dark energy is greater than the gravitation from the masses available in the universe. May be the mean density of the universe is less than the critical density, due to which the masses present in the universe can never produce gravitational contractions greater than the pushing forces. In such cases, the universe will expand continuously forever on a divergent path. As a result, the universe will infinitely large. Every heavenly object grows move away from others and remain alone. Such a scenario is called heat death or also called big freeze. It means any form of available energy has moved to the place of low energy. No more work can be done in Fig: close universe Fig: open universe Fig: flat universe If mean density of the universe is greater than critical density then the universe shrink into spherical shape called close universe. MEMORY TIPS The open universe is curved like a surface of a saddle. MEMORY TIPS

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 311 universe. The hypothesis in which every single matter moves infinitely far away from each other and every form of energy is uniformly distributed already is called big freeze. If the Hubble’s constant keeps increasing then the expansion of the universe will be infinitely large that can rip apart the stars, atoms, space and time into nothingness. The term for such a hypothetical scenario is a big rip. Therefore, the universe is said to be an open universe in case the masses in the universe cannot produce gravitation to slow down the expansion of the universe as a result the expansion continues until all heavenly objects are alone. FACTS WITH REASONS Every heavenly object will be alone, cold and frozen in an open universe. Expansion force is stronger than gravitation in an open universe. As a result, every heavenly object will be continuously pushed apart by expansion force until they are alone, cold and frozen. ACTIVITY 6 Make a 3D model of the open universe. Flat universe As discussed above, the universe will be closed if gravitation can counter the expansion of the universe and the universe will be open if gravitation cannot counter the expansion of the universe. However various experiments have suggested that the universe can be flat. The concept of the flat universe is a dividing line between open and close universe. Let’s suppose the mean density of the universe equals the critical density then the masses in the universe can produce gravitation which is exactly equal to the expansion of the universe. Then the gravitation will significantly counter the expansion. The rate of expansion will decrease slowly. However, the universe keeps expanding because gravity is not strong enough to actually stop the expansion. In case, dark energy exists, then we can assume that even though gravitation tries to slow down the expansion at first, it cannot do so forever. Therefore, eventually, the universe will slowly but surely keeps expanding. The flat universe is more stable and lasts longer than any other model of the universe. The expansion of a flat universe does not disturb the formation of stars, solar systems and galaxies. In case the flat universe dies it will be similar to the open universe. Therefore, the universe is said to be a flat universe, in case the gravitation can slow down the expansion from big bang but in an infinitely long time so that formation of stars and galaxies is possible. Graphical representation of types of universe We have discussed the types of universe based on their shape. Here, we will show these universe in the graph. If mean density of the universe is less than critical density then the universe expand into saddle shape called open universe. MEMORY TIPS If mean density of the universe is equal to the critical density then the universe will be flat shape called flat universe. MEMORY TIPS

312 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Open Flat Close omega point alpha point Radius of the Universe now time Fig: Types of universe FACTS WITH REASONS The stars and galaxies exist even though the flat universe is expanding. The stars, solar systems and galaxy exist even though the flat universe is expanding because in this universe expansion and gravitation are almost equal. The universe keeps expanding however the gravitation is just sufficient enough to form stars and galaxies. ACTIVITY 7 What evidence suggest that the universe is flat? Discuss with friends. Use Wikipedia to confirm the conclusion of your discussion. HOT SKILL HIGHER ORDER THINKING SKILL 1. Gravitation forms galaxies. Gravitation brings matter together. The stars are heavenly objects with a tremendous quantity of mass. So, the stars can pull each other and stay as a cluster. Sometimes a dying massive star can change into a black hole. Black holes produce enough gravitation to attract stars around them. As a result, billions of stars stay together. Such a cluster of billions of stars is called a galaxy. Hence, we can conclude that gravitation can form galaxies. 2. The earth revolves around the sun. The earth and the sun both have mass. So, there must be gravitation between them. The gravitation between the sun and the earth makes the earth revolve around the sun. 3. Compare between the open universe and the close universe. The comparision between the open universe and the close universe are listed below:

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 313 SN Open universe SN Close universe 1 In this universe, the matter will continue to expand forever in divergent path. 1 In this universe, the matter will continue to converge. 2 The expanding force (big bang force) is greater than gravitation. 2 The gravitation is greater than expanding force (big bang force). 3 The open universe is curved like the surface of the saddle. 3 The closed universe is spherical or elliptical. 4. The moon does not collapse into the earth. The moon does not collapse into the earth because the gravitational pull (centripetal force) between the earth and the moon equals the centrifugal force (inertia of motion) of the moon. As a result, the moon moves around the earth instead of falling into it. 5. Stars of the same constellation remain relatively at the same distance from each other despite the universe is expanding. The stars of the same constellation remain relatively at the same distance from each other despite the universe is expanding because the gravitational pull among the stars is slightly greater than the force that causes the universe to expand. As a result, they remain relatively in the same place to each other. 6. The velocity of Jupiter in its orbit is slower than the velocity of mercury in its orbit. The velocity of Jupiter in its orbit is slower than the velocity of the mercury in its orbit because Jupiter is very far away from the sun compared to mercury. So less gravitational force acts on Jupiter than on the mercury. As a result, Jupiter has a smaller velocity of revolution. 7. Why don’t planets collide while orbiting around the sun? The planets do not collide even though they are orbiting around the sun because they have their fixed orbit. They have already cleared other obstacles in their path. 8. What are the conditions required for a universe to be either flat or closed or open? The conditions required for a universe to be flat are: i. If mean density of the universe is equal to the critical density. ii. If gravitation produced by masses equals expanding forces (big bang force). The conditions required for a universe to be open are: i. If mean density of the universe is less than the critical density. ii. If gravitation produced by masses is less than expanding forces (big bang force). The conditions required for a universe to be closed are: i. If mean density of the universe is more than the critical density. ii. If gravitation produced by masses is more than the expanding forces. 9. Even though the universe is expanding, the galaxy does not expand. Even though the universe is obviously expanding the solar system does not expand. It is because the gravitational attraction between the stars and the black hole is strong enough to hold itself together. They act as a single unit in the space. So, they do not expand. 10. What would be the shape and fate of the universe based on its density? The fate of the universe based on its density is listed below:

314 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur i. If the density of the universe is less than the critical density, the universe will be open. It expands forever because gravity is weaker than expanding force. So, the universe ends in a big chill or big rip or heat death. ii. If the density of the universe is more than the critical density, the universe will be closed. It contracts forever because gravity will be stronger than expanding force. So, the universe ends in a big crunch. iii. If the density of the universe is equal to the critical density, the universe will be flat. It expands but slowly. It will last longer than the other model of the universe. However, it will end in a big chill or big rip similar to the open universe. 3 STEPS 3 STEPS EXERCISE EXERCISE STEP1 1. Select the best answers from the given alternatives a. What puts the planets around the sun despite the universe is expanding? i. magnetic forces ii. dark energies iii. gravitation iv. expanding forces b. What’s the conclusion of Hubble’s observation? i. galaxies far away are red ii. galaxies travel faster iii. universe is expanding iv. there are many galaxies around us c. How will our world end if the gravity produced by galaxies will slow down the expanding force? i. every matter in the universe will concentrate at a single point ii. every matter in the universe will spread out until they are all alone iii. the universe will be flat iv. the universe will be divergent d. How will an open universe die? i. it will end with a big crunch ii. it will end as a hot ball of matter iii. it will be cold and dark iv. it will die in a big chill e. Which universe has negative curvatures? i. close universe ii. open universe iii. spherical universe iv. flatuniverse f. Why does the moon revolve around the sun? i. gravitation ii. gravity iii. terrestrial magnetism iv. van der wall force

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 315 2. Define the following terms with required examples. a. Universe b. Gravitation c. Big crunch d. Galaxy e. Black hole f. Big bang theory f. Close universe h. Open universe i. Flat universe 3. Answer the following questions in very short. a. What causes satellites to revolve around the planet? b. Who and when proposed the big bang theory? d. What kind of universe has positive curvature? e. Which model of the universe allows particles to unite into a point? f. Which hypothesis on the origin of the universe is most valid yet? g. What will the universe be like if the gravitation balances expansion just right? h. Is our universe close, open or flat, what does the observation suggest? i. What is the meaning of H in Hubble’s law, v =Hd? STEP2 4. Give reasons: a. Satellites revolve around the planet. b. Gravitation forms galaxies. c. The big bang theory is the most reliable. d. Black holes can form galaxies whereas stars can form solar systems. e. Excessive gravitation can produce a close universe. f. Open universe is formed if gravitation is weaker. g. Balance between gravitation and expansion forces is key to a flat universe. h. A closed universe will end with a big crunch. i. An open universe will end with a big freeze. j. A flat universe end with a big freeze. 5. Differentiate between the following. a. Close universe and open universe b. Flat universe and close universe c. Gravitation and momentum from the big bang 6. Answer the following questions in short. a. Enlist the effects of gravitation.

316 univeR Se Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur b. What is the role of gravity in the formation of the solar system? c. Is the universe expanding? Put your opinion with a suitable explanation. d. What happens to the universe if the mass present in the universe produces gravitation stronger than the expansion forces? Explain. e. What happens to the universe if the mass present in the universe produces gravitation weaker than the expansion forces? Explain. f. Describe the big bang theory. h. How do Hubble’s observations support the big bang theory? STEP3 7. Observe the given diagram and answer the following questions. a. Answer the following questions on the basis of the given figure. i. Which model of the universe is the above picture trying to represent? ii. What are required conditions for the creation of such a universe? iii. How will such a universe come to an end? iv. What is the relation between density of this universe with critical density? 8. Answer the following long questions. a. What is the proof of the big bang? How did the universe come to be based on the big bang theory? b. What end awaits the open universe? Explain. d. What are the conditions for a universe to be closed, open or flat? Write the features of each model of the universe. e. What would be the fate of the universe based on its critical density? How will a close universe and a flat universe meet their end? f. Based on the big bang theory, universe is expanding. Does it expand forever? Put your opinion and support your opinion with a scientific reason.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 317 1. ICT : Information and Communication Technology (ICT) is a complete term that includes all the technologies and services involved in computing, data management, telecommunications facility and the internet. 2. Signal : A signal is an electromagnetic or electrical circuit that is used for carrying data or information from one source or device or network to another. 3. Analog signal : Analog signal is a continuous electrical signal having continuous value (variable) with time. 4. Digital signal : Digital signal is a non-continuous electrical signal having discontinuous (discrete) values with time. 5. Bit : A bit is the smallest unit of computer memory which has the capacity to store a maximum of two different values 0 or 1. 6. Bit rate : The bit rate refers to how many bits are transferred in every second. 7. Byte : Byte is the basic unit of computer data storage in the set of 8 bits. 8. Digital signal transmission: Digital signal transmission is the process of sending information over physical communication media in the form of digital signal. It is also known as digital transmission. Key terms and terminologies of the unit Sequence of Curriculum Issued by CDC  Digital signal and introduction to bit and byte  Digital signal transmission  Positive and negative impacts of digital technology in daily life  Concept of Netizenship, online reputation, and digital wellbeing  Preparation and presentation of audio or audio-video material  Recording of audio and audio-video from mobile phones or computers  Audio or audio video editing (cutting and joining only) UNIT Information and Communication Technology (ICT) 13 Estimated teaching periods Theory Practical 5 5 Claude Elwood Shannon is known as the father of information theory for his contributions to telecommunications. He was born in the United States of America on 30th April 1916 and died on 24th February 2001. He was a mathematician, electrical engineer and cryptographer. He invented the branch of science “information theory”. He contributed to enabling telecommunications to move from an analogue to a digital transmission system. Claude Elwood Shannon About the Scientist

318 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 9. Baseband transmission: Baseband transmission is the method of sending a digital signal over a channel without changing the digital signal to analog signal. 10. Broadband transmission: Broadband transmission is the method of sending a digital signal over a channel after changing the digital signal to analog signal after modulation. 11. Netizen : The person who uses internet for any purpose is called netizen. 12. Netizenship : Netizenship is the set of best practices that describes how a person surfs safely, ethically and appropriately on internet. 13. Netiquette : Netiquette (Digital Wellbeing) is a set of guidelines or socially acceptable behavior that a netizen has to follow while using internet. 14. Online reputation: Online reputation is the way that a person or business is perceived based on the information that appears about them online. 15. ORM : Online Reputation Management (ORM) is the process of managing the accurate and sustainable online information about a person, company or a brand. Introduction Information and Communication Technology (ICT) is a complete term that includes all the technologies and services involved in computing, data management, telecommunications facility and the internet. These technologies deal with the transmission and reception of information of various kinds. ICT has numerous applications. For example, it enhances the modes of communication, it reduces cost, it eliminates the usage of paper, it provides a better teaching and learning methods, it enhances the data and information security, it minimizes cost and saves time etc. In this unit we will discuss about digital signal and its transmission; impacts of digital technology in daily life; netizenship; online reputation; digital wellbeing and many more. ICT is the technology that supports various activities of information and communication such as gathering, processing, storing and presenting data. Signal A signal is an electromagnetic or electrical circuit that is used for carrying data or information from one source or device or network to another. It is the key component behind telecommunication, computing, networking and electronic devices. Besides these, signals are also used to communicate and send instructions by processors, memory, storage and numerous other components. A signal can be either analog or digital. Each signal carries data in some form. It is created when a command or data is sent to a device. Analog signal Analog signal is a continuous electrical signal having continuous value (variable) with time. These kinds of signals work with physical values and natural phenomenon such as earthquake, frequency, volcano, speed of wind, sound, temperature, etc.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 319 Fig: analog signal Digital signal Digital signal is a non-continuous electrical signal having discontinuous (discrete) values with time. This kind of signal is used in all digital electronics including computer, mobile and data transmission devices. Digital signals are represented by binary numbers 0 and 1. The combination of these binary number represent the digital signal. One binary number has only two possible combination, two binary numbers make four possible combination and three binary numbers make eight possible combination. Number of digit Possible combination 1 0 and 1 2 00, 01, 10 and 11 3 000, 001, 010, 011, 100, 101, 110 and 111 Time (seconds) 0.5 1 Amplitude (volts) Fig: digital signal FACTS WITH REASONS The graph of digital signal is discontinuous, why? The graph of digital signal is discontinuous because it has series of low and high potential with ‘0’ and ‘1’ values respectively. The low potential or ‘0’ values make the graph discontinuous or discrete. Analog signal is represented by sine waves while digital signal by square waves. MEMORY TIPS

320 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Differences between digital signal and analog signal S.N Analog signal S.N Digital signal 1. Analog signal is a continuous electrical signal having continuous value (variable) with time. 1. Digital signal is a non-continuous electrical signal having discontinuous (discrete) values with time. 2. Analogue signals can not be represented by binary numbers 0 and 1. 2. Digital signals are represented by binary numbers 0 and 1. 3. Graphically, analogue signals are represented by sign wave. 3. Graphically, digital signals are represented by square wave. 4. ADC (analogue digital converter) converts digital signals into analogue signal. 4. DAC (digital analogue converter) converts analogue signals into digital signal. Concept of Bit and Byte Bit A bit is the smallest unit of computer memory which has the capacity to store a maximum of two different values 0 or 1. It is actually a single unit of information reflecting a zero (off/false) or a one (on / true). It is an abbreviation of binary digit. Bit forms the basis for all larger data in digital technology. Since computer and other computing devices communicate using binary states, they do not understand anything smaller than ‘1’ or ‘0’. Bits are primarily used to represent data used and speed of technology of internet, telephone and streaming services. The bit rate refers to how many bits are transferred in every second. A bit is represented by a small letter ‘b’. Byte Byte is the basic unit of computer data storage in the set of 8 bits. There are altogether 256 distinct combinations of these 8 bits. These combinations cover the alphabets, special characters and many more. When we talk about the quantity of information in the computer’s memory, we especially talk about bytes. Each byte acts as one unit each of this unit is made up of the eight bits. A byte is represented by a capital letter ‘B’. Differences between Bit and Byte S.N. Bit S.N. Byte 1. Bit is the smallest and fundamental unit of computer data system. 1. Byte is the basic unit of computer data storage which is the set of 8 bits. 2. Bit stands for binary digit. 2. Byte stands for binary elementary string. Do you know that ‘0’ of digital signal represents ‘low voltage’ and ‘1’ represents ‘high voltage’? MEMORY TIPS 1 Byte = 8 bits Digital electronic devices use digital signal for their operation. MEMORY TIPS

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 321 3. It is used to measure electrical signals, transmission speed of internet, telephone and streaming services. 3. It is used to measure size of data like photos, videos, documents,etc. 4. It is denoted by ‘b’. 4. It is denoted by ‘B’. 1. ASCII stands for American Standard Code for Information Interchange. 2. ASCII was first developed in 1963 by American Standards Association MEMORY TIPS Digital Signal Transmission Digital signal transmission is the process of sending information over physical communication media in the form of digital signal. It is also known as digital transmission. In this transmission the signals vary separately with time. It uses two-state logic represented by two levels of electrical voltage, one high (represented by 1) and one low (represented by 0). For example, the light switch can only take two values or state: open or closed, or on or off. We can transmit a digital signal by using one of two different approaches. They are baseband transmission and broadband transmission (using modulation). A. Baseband Transmission Baseband transmission is the method of sending a digital signal over a channel without changing the digital signal to analog signal. It requires low pass channel for its transmission. A low pass channel is a channel whose bandwidth starts from zero. Each signal uses the entire bandwidth of channel to send information in baseband transmission. It also uses bidirectional transmission of data. Baseband transmission uses twisted-pair cables, coaxial cables and wires as the medium of transmitting digital signal. Advantages of baseband transmission i. It is easier to use because of its simple structure. ii. It has low cost installation. iii. It has easy installation and maintenance. Disadvantages of baseband transmission i. It is used in limited distance transmission. ii. It can be used only for data and voice. iii. It has short coverage and limited range. 1. The combination of 00100001 and 00100010 of 8 bits code for the characters ‘A’ and ‘B’ is I ASCII code. 2. Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte are the multiples of byte. MEMORY TIPS 1. Channel is a separate path through which electrical signal can flow. 2. Bandwidth is the maximum amount of data transmitted over an internet or between computers in a specific time. MEMORY TIPS Low pass channel or baseband channel is a communication channel that can transfer frequencies that are very close to zero. MEMORY TIPS

322 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Uses of baseband transmission It is mostly used for the LAN (Local Area Network) Networks as the baseband signaling can transmit the digital data for a short distance. B. Broadband Transmission Broadband transmission is the method of sending a digital signal over a channel after changing the digital signal to analog signal after modulation. It uses bandpass channel. A bandpass channel is a channel whose bandwidth does not start from zero. A bandpass channel is available more than a low pass channel. Many signals with various frequencies can be transmitted simultaneously. It uses unidirectional transmission. Broadband transmission uses optical fiber cables, co-axial cables and radio waves for its transmission. Advantages of broadband transmission i. It supports the transmission of data, voice and video. ii. It offers greater bandwidth. iii. It can be used for long distance transmission. Disadvantages of broadband transmission i. Its cabling is complex. ii. Its maintenance is quite difficult. iii. Its installation cost is expensive. Uses of broadband transmission It is mostly used for the telephone network as the broadband signaling. It can be transmitted for a long distance. Components of digital communication system There are following components of digital communication system. Source For digital communication the source is analogue signal. Input transducer It converts input signals into electric signal. For example, microphone converts sound into electricity. Encoder It converts data into minimum bit number. It helps easy transmission of signals. Modulator It modulates signals and converts into analogue signal. After converting into analogue signals, modulator gives direction to pass into medium or channel. Modulation is a process of converting a digital signal to analog signal or viceversa. MEMORY TIPS Bandpass channel is a communication channel whose bandwidth does not start from zero. MEMORY TIPS Amplitude Bandpass channel Frequency f1 f2 Broadband Transmission

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 323 Channel Channel or medium provides path for analogue signal from transmitter to the receiver. Demodulator It demodulates signals obtained from receiver. Decoder It digitized the demodulated signals so that there will be less error in the output signals. Output transducer It converts decoded signals into original physical quantity. For example, loud speaker converts electricity into sound. Output signal It is the result of signal transmission process. For example, if sound is transmitted from the source then the output is also sound. Fig: Components of digital communication system Differences between analogue communication and digital communication S.N. Analogue communication S.N. Digital communication 1. Analogue communication transfers data with the help of analogue signals from transmitter to receiver. 1. Digital communication transfers data converting analogue signals into digital signal and finally into analogue signal.

324 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 2. Analogue communication passing through channel is affected by outer factors. 2. Digital communication passing through channel is less affected by outer factors. 3. Coding is not possible in this communication. 3. Coding is possible in this communication. 4. It needs less bandwidth. 4. It needs more bandwidth. Advantages of digital transmission 1. Designing of digital circuit is easy and chief compare to the analogue circuit. 2. Digital transmission is less affected by outer factors or noise. 3. We can believe in the circuit used in digital transmission. 4. There is less overlapping and less crossing in the transmission of digital signals. 5. By using encoding and compression, we can protect the security of the information. 6. There is less chance of fault in digital signal transmission. 7. Generally there does not occur changes in the characteristics of the digital signals. Effects of digital technology in the development of information and communication Even though digital technology is getting better, information and communication are getting better as well. Digital technology is used more in telecommunications, the internet, digital media, digital TV, and other areas. 1. Digital telecommunication There is fast communication due to digital telecommunication. As a result, we can run many telephone together. 2. Digital media The medium through which electronic devices are used is called digital media. With the help of these electronic devices we can see news, send online information, create digital media, etc. 3. Digital TV The high definition TV are made due to the use of digital technology. It is used to broadcast news, information, etc. throughout the country. Effects of Digital Technology in Human Life The 21st century has been called the era of Science and Technology. Various new technologies have been developed and advancement over the last few decades. Digital technology has advanced more rapidly than any other innovations in our history. Nowadays people are using technology regularly without rest. One cannot even imagine of living without a smart phone or their laptops. In various sectors like food, education, health, entertainments, etc. digitization has been done upto its maximum possibility. But we know that every technology has some positive and negative aspect side by side. Here, we discuss some of the impacts of digital technology on human life.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 325 A. Positive aspects of digital technology Digital technology and computing world have made their way into more areas of life, from communication to finance to social interaction. We can see its uses in home, schools, offices, hospitals, etc. Some of the positive aspects of digital technology in our daily life are discussed below. 1. Education Education is one of the most valuable aspects that the internet has brought to us in a new and improved way. Students of all ages and abilities do not necessarily need to depend on physical classrooms to gain education. They can learn digitally through Google, YouTube, Online Classes and so on. Almost all the schools and colleges have developed their own websites and apps where all the information and details are made available. Such information can be received by every person from home with 24 hours of accessibility. 2. Social Network Social media like Facebook, Instagram, Whatsapp, Viber, etc. have made easier to connect other people and expand our social circle. Social media also enables people chat or call with one another. They can share their photos, videos and watch their lives unfold in real time which remain saved as a memory in one’s life. It has enabled us to share more parts of their lives than ever before. 3. Banking sector and beyond the Bank Banking sector has become easy with the development of digital technology. People have access to perform almost all the activities of the bank by online mode. Money transaction, online payment, balance inquiry, any sort of query can be easily done by the applications developed by different banks. Furthermore, no one has to wait in the long line of banks for paying their utility bills. e-Sewa, Khalti, Phonepay, etc. are the technologies beyond the banking sectors which have facilitated us with its different features. Such apps allow us to perform online

326 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur payment in any fields, such as online booking of means of transportation, entertainment and so on. 4. Business Business is also one of the most important services provided by the internet. Using different apps, online customers can purchase almost everything at any time from the comfort of their own home. Digital technology has also enhanced the expansion of their business to different parts of their own country and abroad. Advertisement of their products on the internet can easily reach to millions people within a minute. For example, Daraz, Foodmandu, Pathao, etc. run their online business and are benefitted with. 5. Health Internet access to health information provides quality of care, 24 hour access to medical or health information and allows more efficient handling of special health issues. Inventions of different equipment use digital technology for the diagnosis and treatment of diseases. People use information shared on internet to prevent themselves from different diseases and to communicate with medical practitioners. 6. Digital technology in other sectors Mobiles, tablets and laptops are also used in several other sectors. Playing games, watching videos, conducting online meeting, access to calendar, online and offline dictionary, etc. are also the aspects that people are benefitted with. Thus, digital technology has made most of the aspects of our life convenient and accessible by connecting us globally through networking. B. Negative aspects of digital technology It is obvious that digital technology have become an integral part of our daily life. Not only merits but also several demerits are associated with digital technology. Technology addiction, time loss, cybercrime, isolation, poor academic performance, health issue, etc. are several side demerits of digital technology. Few negative aspects of digital technology are discussed below. 1. Psychological effects Overuse or dependency on technology may have adverse psychological effects. It includes isolation form family and friends, depression and anxiety which make a person mentally ill. 2. Physical health effects Regular and continuous use of digital technology may increase the risk of eyestrain, poor posture, sleep problem, obesity, reduced physical activities, etc.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 327 3. Learning Barriers Students and people have slowly stopped to remember information because they know they can find it online within seconds. It is also found that students are more likely to remember where to get the information rather than remembering the information itself. 4. Cyber bullying Cyber bullying is the use of the internet, cell phones, video game system or other technology to send or post messages to hurt or humiliate or threat someone else. 5. Terrorism and crime There are many people on the internet who use the dark web to do illegal work. The identity of a person can be made hidden and it becomes difficult to track the person or organization on the dark web. So by using dark web some people do buying and selling of illegal drugs, weapons, duplicate electronic accessories, blackmail, creating and promoting the robbery groups, doing the criminal works, etc. It is the misuse of the digital technology. 6. The concern for privacy and manipulation of digital data The activities like stealing, editing and posting photos, videos and digital data of third person have increased the risk of privacy and manipulation of digital data. Many of these negative impacts of technology can be avoided with the increase of awareness program on cyber education. This education not only provides a greater awareness of one’s own actions, but also helps the users to recognize the action of others. Netizen and Netizenship Netizens (digital citizens) are the people having an active participation in the online community of the internet. The person who uses internet for any purpose is called netizen. In this digital world, almost every person is a netizen. Netizenship is the set of best practices that describes how a person surfs safely, ethically and appropriately on internet. Netizenship includes the best practices of netizens to use the internet effectively, scientifically and without compromising their security. Characteristics of good netizen A good digital citizen (netizen) knows which types of websites, apps, and online interactions are avoidable and what types of websites are reliable sources of information. A good netizen must be very careful while dropping off comments on Facebook, Instagram or Twitter so that it may not put us at risk or harm others. A good netizen should not share others’ private message, pictures, videos, etc. to the whole world without the consent of the person. A good netizen should not download, copy or share other’s data without author’s permission or unless it is free. A good netizen should never criticize someone else without knowing the truth about the issue. Receiving hateful messages or threatening messages, warnings, virus, password stolen and internet polling are the major forms of cyber bullying among school children in Nepal. MEMORY TIPS Digital footprint is a data that is left behind by a netizen while using internet. MEMORY TIPS

328 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur FACTS WITH REASONS Why does digital footprint important? i. Digital footprint is important to determine person’s digital reputation. ii. It is important to check employee’s activities especially in social media before hiring. iii. It is important to check for the words and photos that are posted online. It may cause unintentional offence when gets altered by others. Digital Wellbeing (Netiquette) In today’s digital world, we have seen more and more manner issues like spreading fake news, cyberbullying, trolling and many more. Thus, all netizens must follow some internet etiquette (netiquette) while surfing internet. Netiquette is a set of guidelines or socially acceptable behavior that a netizen has to follow while using internet. i. Be aware of what you post and comment: A netizen must be very careful while dropping off comments on Facebook, Instagram or Twitter so that it may not put us at risk or harm others. ii. Respect others’ privacy: A netizen should not share others’ private message, pictures, videos, etc. to the whole world without the consent of the person. iii. Avoid sharing fake news: Any types of information should be checked for their reliability before sharing. Fake news may make others to take bad decision or even may create panic. iv. Respect copyright: Copyright is a legal means of protecting an author’s work. A netizen should not download, copy or share other’s data without author’s permission or unless it is free. v. Honour the owner: Honour the owner when sharing someone else’s words, pictures or other forms of intellectual property by mentioning the source or reference. vi. Avoid internet crimes: Cyberbullying is a terrible crime. A netizen should never criticize someone else without knowing the truth about the issue. Such activities can cause the person to be mentally and emotionally depressed. vii. Share beneficial knowledge: A netizen should always share useful information and avoid harmful information to prevent miscommunication and misunderstandings. viii. Recognize and respect diversity: People with different cultures, opinions, lifestyles and perspectives are connected together through internet. A netizen must respect other before posting views related to sex, religion or politics. ix. Use your influence wisely: A netizen does not have right to judge others even if a person has millions of followers. A netizen should always practice proper netiquette while using internet. One should always aim to a better netizen.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 329 Online Reputation We see various things that are present in online. After their observation we like, share and comment on it. In the same way we see what others have shared and commented about us. It shapes what other people think about us. This is our online reputation. Our online reputation could affect how people think about us or even behave towards us. Online reputation is the way that a person or business is perceived based on the information that appears about them online. Online reputation is the opinion of users of the brand present in the internet. It is given either through reviews in search engines, opinions in forums or publications on social network. It is based on their own experiences. An online reputation is so vital that a single misstep can cause a loss of revenue and trust in the brand. Factors affecting Online Reputation i. Bad reviews: Bad reviews always act as repellent for the customers towards the brand. ii. Social media: The negative comments are rapidly spread through social media. They affect reputation of an individual or of an organization. iii. Technological problems: Technological problems occurred in the server of the company (financial or institutional) affect their reputation. iv. Spread of misinformation: Spread of misinformation about the individual or company through internet can quickly damage a reputation. v. Security breaches: An organization loses its reputation if it is unable to protect or secure its digital data from being hacked and manipulated. FACTS WITH REASONS How does online reputation affect the rise and fall of a company or a business? Nowadays about 85% of the consumers give their opinion or reviews through online. About 91% of the consumers are more likely to choose business/brand/company with five-stars ratings. About 82% of the consumers are less likely to choose business/brand/company with negative reviews. Online Reputation Management (ORM) Online Reputation Management (ORM) is the process of managing the accurate and sustainable online information about a person, company or a brand. To prevent an organization from being the victim of reputation loss, it is very convenient to perform the following actions. i. Monitor: Always check for the negative comments or attacks on the online reputation of the brand. ii. Attend: Always respect and give importance to the opinions of users and followers. iii. Communicate: Always give correct information and content of the company on the internet. Online reputation is judged from the likes, shares and comments about a person, company or organization. MEMORY TIPS One can lose online reputation, if digital etiquette is not followed. MEMORY TIPS

330 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur iv. Respond: Always answer the questions and doubts obtained from the users and followers, especially the negative ones, in a correct and polite manner. v. Apology: Any occurrence of errors in company’s content or information must be evaluated, corrected along with the apology for the incorrect information. FACTS WITH REASONS Why is online reputation management important? The online reputation management (ORM) is important to establish an accurate, sustainable and controllable background about the company, brand, organization or a person. ACTIVITY 1 Visit any five companies or organizations in your neighborhood. Take inquire about the digital technology used for the promotion or implementation of their business. Present the data collected in the tabular form as shown below. S.N. Name of the organization or company Name of the Digital Technology used Digital Technology is used for Problems faced by using technology Steps taken to solve the issue 5. XYZ School School’s Website To provide the information of the school, latest events, contacts and so on. Negative comments by some users. Responding to the comments or suggestions or complaints wisely and punctually. 2. 3. 4. 5. Audio-visual recording Recording of audio and visual is one of the activities that everybody does in phone or computer. The purpose of the recording varies according to the person and their work. A businessman records for the promotion of his business, a film maker records for entertainment, a scientist records for his research, a student records for his study, trips, school programs and so on. Every person must have knowledge of recording their audio and video. Here, we discuss some the methods to record audio and video through phone and computer. To prevent an organization, brand and person from being victim of reputation loss, Online Reputation Management(ORM) is necessary. MEMORY TIPS

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 331 Audio Recording A. From laptop and computer All laptops and some computers have in-built microphone while rest of the computers do not have. We need to use head phone having microphone to record sound in such computers. We can follow the following steps to record sound. Step 1 : Open ‘Sound Recorder’ application in your device. You can find ‘Sound Recorder’ application in the following location. Start > All Programs > Accessories > Sound Recorder Step 2 : Click ‘Start Recording’ to begin recording. Step 3 : Click ‘Stop Recording’ to stop recording process. Step 4 : You can give filename and choose destination in the window where it is to be stored. Step 5 : Click ‘Save’ for its future use. B. Voice Recording in an iPhone All iPhones have in-built voice recording application which cannot be deleted. To record voice or sound, you can follow the following steps. Step 1 : Open the ‘Voice Memos’ application. Step 2 : To begin recording, press the red record button. Step 3 : To stop recording, press the red stop button. Step 4 : Tap ‘Done’ after you finish recording. Step 5 : Type a file name for the recording Step 6 : Press ‘Save’. By following these steps, your sound will be recorded and saved permanently for future use unless it gets deleted. C. Voice Recording in an Android Phones Most of the android smart phones are provided with a bundle of in-built software. It includes a voice recording program like ‘Recorder’, ‘Voice Recorder’, ‘Memo’, ‘Notes’, etc. Some of the smart phones lack voice recording application. So, in this case, the application can be downloaded from the Google Play Store. You may search for ‘Voice

332 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Recorder’ and ringing application that meets your needs. The steps mentioned below can be followed to record and save your audio file. Step 1 : Locate or download a voice recorder application on your phone and click to ‘Open’ Step 2 : Press the ‘Red’ or ‘Record’ button to begin recording. Step 3 : Press the ‘Red’ or ‘Stop’ button to stop recording. Step 4 : Click on ‘Save’ button. A window with few details opens up. Step 5 : Type the file name and click on ‘Save’ button. The above mentioned steps will assist you to record and save audio file in your android smart phones. D. Voice Recording directly from the Web or Internet Voice or Sound can be recorded directly from the internet or web. There are many web-based voice recording tools in the web such as Online Voice Recorder.: https://online-voice-recorder. com/beta/. You may follow the following steps to record your audio directly from the internet. Step 1 : Go to https:// online-voicerecorder.com/ beta/ from any web browser. Step 2 : Click on ‘Allow Microphone Access’. You can click on ‘Setting’ button to organize your microphone. Step 3 : Click the red ‘Record’ button to begin recording. Step 4 : Click ‘Stop’ button to end the recording. Step 5 : Click on ‘Save’ to save your file. Cutting and Joining of Audio and Audio-visual Media A. Cutting audio or MP3 media on Android When we listen to music or any audio, sometimes we get too much attraction by some portion of the track. We may like to join such selected portions together in one single audio. In these cases, cutting the audio file is the first and the most important part. Audio cutting feature is missing in most of the android devices. So to assist the cutting process, Music Editor, MP3 Cutter, Ringtone Maker or Song Editor applications can be downloaded and installed in the device. These applications are available for free on Google Play Store. To cut the portion of audio, you can follow the steps given below.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 333 Step 1 : Open the Music Editor application. Step 2 : Choose ‘Trim Audio’. Browse you music library to locate the file you want to edit and load it into the editor. Step 3 : Play the music in the editor. Mark the starting and ending of the audio to be cut. Step 4 : Click on ‘Save’ button at the top right corner. Step 5 : Give file name to the edited audio. Audio can be cut or trimmed online by using several online applications like Audio Cutter Online, Online MP3 Cutter and so on. The following steps can be followed to trim or cut audio online. Step 1 : Open the Online Cutter application. Step 2 : Choose or browse a file that you want to cut (or drag and drop your Online audio/video cutter/trimmer is available in internet and can be used free of cost. MEMORY TIPS

334 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur file, or upload from Google drive). Step 3 : Select the interested music from the track by dragging the interval control. Step 4 : Then ‘Download’ or ‘Save’ the selected or trimmed audio. You also can perform some other editing like changing pitch, volume or speed of the audio. Merging or joining audio files into one (Online) Two or more audio files can be merged into one through online application like Online Audio Joiner. It works in a browser window and you can join MP3 and other format files without installing software in your computer. The steps given below can be followed to merge two or more files into one. Step 1 : Open online joiner website. Step 2 : Click on ‘Add tracks’ button to upload the audio files that you want to merge. You can upload unlimited audio files that are to be merged. Step 3 : Set the order of the audio files by pressing the arrow key. Step 4 : Click on ‘Play’ button to check the correctness of the order of the songs. Step 5 : Click on the ‘Join’ button to merge the added audio. Step 6 : After the files are merged, you may download the merged audio. It gets saved in your computer. Merging or joining audio files into one (Offline) There are few offline applications which can merge two or more audio files into one. For example, Audacity, Streaming Audio Recorder, Merge MP, etc. Here, we will discuss about Merge MP application because it is quite easier to use as compared to others. Merge MP3 is a portable tool that is extremely easier to use. It supports only MP3 audio format. The following steps are followed to merge two or more audio files into one. Step 1 : Open the ‘Merge MP3’ application. Step 2 : Go to ‘File’ menu and click on ‘Add Files’ option. You may manually select audio files to be merged. Step 3 : After adding the audio file, click on ‘File’ button and select on ‘Merge’ option. Step 4 : Type a filename and save it to the required folder. Video Recording, Cutting and Joining A. Video Recording Video recording is the process of storing a video in a recording medium such as magnetic tape, optical disc, or a computer memory. 1. Video Recording in an Android Device: With an android phone, you can record, edit and share videos. In android phone, it is easier to learn how to record a video. There are

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 335 varieties of android devices available in the market. Every android device has their own settings and features. The steps given below can be used to record the video. Step 1 : Open the camera of your device. Step 2 : Once you are in camera, scroll along the bottom of your screen to find the video file. Step 3 : Press the record button on your screen to start the video recording . Step 4 : Press stop button (the same record button) to end the video recording. Some of the devices save the video automatically while others ask your permission. So you may press on ‘save’ button in such case. To find your recorded video, search either a videos application or a file application or gallery application. 2. Online Video Recording through application: There are several video recording applications available in the internet free of cost. applications like Droplr, FilmoraGo, XRecorder, Screencast-O-Matic, Vidma Recorder, Screencapture.com, etc. Such applications are provided with tutorials for their uses. Every video recording application can be used easily as per the settings and features of the application. Source: https://hotmart.com/en/blog/video-recording-apps B. Video Cutting or Trimming Video cutting or trimming is the process of removing the clip’s front or tail portions to create a new clip. It can be done through video editing applications both from mobiles and computers. 1. Video cutting in an Android: In an android device, videos can be trimmed using builtin Gallery application. When you cut a video, you will not lose your original video, rather you create a new one. The steps given below can be followed to trim/cut a video. Step 1 : Open the Gallery application on your device and tap on the video that you want to trim. Step 2 : Tap the pencil icon in the bottom left corner to get a new editing screen. Step 3 : Move the sliders at the bottom of the screen to mark the start and end of your video that you want to cut. Step 4 : Tap ‘save’ at the top right corner. Your trimmed video will be save in the Gallery application. Source:https://www.howtogeek.com/201843/how-to-trim-and-cut-videos-on-your-android-device/ 2. Online Video Cutting: Video shooting and editing may be the hobbies of many students where you may have some large video files to cut. In internet, we can find several video

336 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur cutters available for free. For example Gihosoft Free Video Cutter, Free Video Cutter, Media Cope, Video Edit Master, Free Video Cutter Joiner and so on. Almost every application has similar way of editing videos. Here, we discuss about the steps followed to trim videos through Free Video Cutter. Step 1 : Select and upload a video file from your device. Choose a video up to 1 hour long. Step 2 : Trim your clips by sliding the handlebars or by entering the time cuts manually. Step 3 : Instantly download your newly trimmed video clip. C. Video Joining or Merging It is the process of joining or combining of two or more video clips into a single clip. It is done by several applications available in the internet or by using built-in features of video merging in a phone. 1. Video Merging in an Android: Multiple videos can be merged into one by using built-in Gallery application in some of the android devices. To combine two or more videos, one can follow the steps given below. Step 1 : Start the Gallery application. Step 2 : Locate one of the videos that you want to merge. Step 3 : Tap the edit button (having the shape of a pencil) in the lower left

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 337 corner of the screen. Step 4 : Add ‘Tap’ at the top of the screen and then choose a second video to combine with the first one. You can add multiple videos to make a single video file and then tap ‘Done’ when you are ready. Step 5 : Tap ‘Save’ at the top of the screen to save new combined-media video. If built-in applications are not present in the android then, the video merging can be done by installing few free applications in the phone. Such video editing applications are easily available in the internet. For example Video Merge, Kinemaster, Androvid, VidTrim, Video Joiner and so on. Such applications are provided with tutorials for their uses. Every video merging applications can be used easily as per the settings and features of the applications. 2. Online Video Merging in Computer: Some windows of computer are provided with built-in application to combine videos. Several applications are also available in the internet that can be used for joining two or more videos. Applications like FlexClip, Windows Photos application, EaseUS Video Editor, Windows Media Player, VLC Media Player, iMovie, and so on. Here, we discuss the method of merging videos using EaseUS Video Editor. Step 1 : Import the source videos by clicking ‘Import’ button or you may drag the videos to the appropriate area. Step 2 : Add the imported files to the video track by choosing the ‘Add to Project’ option, or you may drag and drop the videos to the track. Step 3 : Click on ‘Export’ to merge the videos. The free version of EaseUS Video Editor enables you to combine any number of MP4 files into one video most simply and securely. Source: https://multimedia.easeus.com/video-editor/ ACTIVITY 2 Prepare a power point presentation on the topic ‘Merits and Demerits of Internet’ and present them in your class. (Please include texts, pictures, audio-visuals, etc. in your presentation) ACTIVITY 3 Make a short video of your school by using the methods of recording, cutting and merging. Present them in your class. (Your video must include clips of school premises, labs,library, playground, different activities with background audio, etc.)

338 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur HOT SKILL HIGHER ORDER THINKING SKILL 1. Digital technology helps to improve health facilities. Digital technology can improvise health facilities for us. For example: i. It can collect lots of data regarding our health. ii. It can be used to make various medical equipment. iii. People can access health information at any time. iv. Doctors can use it to diagnose diseases and prescribe medicines in the outpatient department (OPD). 2. How can we be a reputed netizen? We can be reputed netizens if we are responsible and rational. i. We should value others' views. ii. We should be very careful before posting anything on social networking sites. iii. We should avoid fake news and stop sharing them. iv. We should respect the copyright. v. We should never bully others on social networking sites. 3. Let’s suppose you want to make a video for a school program, how would you do it? If we had to make a video for a school program, we would do it in the following ways. i. Record video: We can use a digital camera to record videos. ii. Cut videos: We can cut certain parts of videos from video-cutting applications on computers or mobiles. Tap the pencil icon in the bottom corner of the screen at the beginning and at the end of the video to be cut. Then click save. iii. Merge videos: Open the application. Select multiple videos to be merged. Then click done. When the video is merged, we can click save. iv. Record audio: We can use mobile devices, laptops or iPhones to record audio. First, we have to launch a voice recorder. Then start the recording. We can pause or stop the recording as required. v. Dubbing: The original sound of the video may not be good. So, we should remove that sound. Then we have to merge that video and recorded audio. It helps to produce a good-quality video for a school program. The method of recording audio and video, cutting and merging them and dubbing may be different based on the applications we use. 4. High-speed internet used in current days is a broadband transmission. Give reason. Many internet service providers use broadband transmission because it increases the bit transmission speed. It is cheaper and faster. It can send information to larger distances. 5. We should practise digital wellbeing. Why? We should practise digital well-being because of the following reason: i. to avoid getting addicted ii. to get good sleep and avoid sleep disorders. iii. improve the real-time relationship. iv. be more engaged, energetic and productive.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 339 6. How do the use and application of social networking sites affect students? Write the merits and demerits of social networking sites on students. Social networking sites affect students. Some merits of social networking sites for students are: i. they can learn fast and communicate easily with others. ii. they can be more empathetic and connected on a global scale. Some demerits of social networking sites are: i. spread of wrong rumours, stress, addicted to media, depression ii. sleep disorders, distracted from studies, many start bullying others or get bullied 7. Why is it necessary to use digital transmission? It is necessary to use digital transmission because: i. It can transfer data without noise. ii. There will be no distortion in information. iii. It can transfer data without interference. iv. It is can be mass-produced. It is cheaper. 8. Children should not use mobile devices, laptops etc. more than 2 to 3 hours per day. Why? Children should not use mobile devices, laptops etc. more than 2 to 3 hours per day because excessive screen time has negative impacts on them. Such as: i. It can increase distress and anxiety in children. ii. It can cause mood disorders in children. iii. Children will involve less in social activities. iv. It will increase depression and hatred in children. 9. Write any two differences between the modulator and the demodulator. The differences between a modulator and a demodulator are: SN Modulator SN Demodulator 1 It is the process of influencing data at the transmitter. 1 It is the process of recovering data at the receiver. 2 The modulation is necessary to add carrier signal and message signal and transfer it. 2 The demodulation is necessary to separate the message signal from carrier signal. 10. Why is it important to manage digital reputation? It is very important to manage digital reputation because: i. Online reputation defines us. People judge us or companies based on online reputation. ii. Customers buy products based on the online reputation of companies. iii. A bad reputation can decrease the chances of good opportunities while a good reputation increases the chance of opportunities. iv. Many people will be observing us and our companies on social media. So, we should maintain our online reputation.

340 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 3 STEPS 3 STEPS EXERCISE EXERCISE STEP1 1. Select the best answers from the given alternatives a. Which number system is a byte? i. the base 6 number system ii. the base 10 number system. iii. the base 2 number system. iv. the base 8 number system b. What does a digital signal possess? i. continuously varying values ii. only two discrete values iii. only 4 discrete values iv. constant values c. How can social media be useful to children? i. It allows students to connect with others globally. ii. It can be used for cyberbullying iii. It requires expensive devices. iv. It can be used for cyber-crime d. Which of the following is the best option for a good digital citizen? i. someone who recognizes that there are rights and responsibilities associated with using the internet and other information technology. ii. someone who is only good at using a computer or mobile device. iii. someone who limits their time on the internet. iv. someone who participates actively and often in social media. e. How many combinations are there in the ASCII code of 8 bits? i. 254 ii. 255 iii. 256 iv. 257 f. What is represented by the habit of posting personal details too much on the internet? i. digital well being ii. cautions for digital well being iii. challenges to digital well being iv. application of digital well being 2. Define the following terms with required examples. a. Digital signal b. Bite c. Byte d. Online Reputation e. Netiquette f. Netizens g. Digital Citizenship h. Digital Electronics i. Netizenship j. Cyberbullying k. Signal l) Digital well being 3. Answer the following questions in very short. a. Write a relation between bit and byte. Write their symbol. b. What is the full form of ASCII? c. Define Internet etiquette. d. List out any two applications that are used to edit audio. e. Write the use of byte. f. What is Online Reputation Management? g. Write the main objective of Online Reputation Management.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 341 h. Write the steps for transmission of the digital signal. i. Write down the audio file format. j. What signal transmission technique does not convert digital signal to analog signal? k. What is the fastest way of sending mail? l. Give two examples of analog signals and digital signals. 4. Differentiate between the following. a. Bit and Byte b. Digital Signal and Analog Signal c. Digital communication and analog communication d. Broad band transmission and baseband transmission e. Netizen and Netizenship f. Netizenship and Netiquette g. Digital well-being and online reputation h. Modulator and demodulator STEP2 5. Give reasons a. Digital invention is one of the major inventions in ICT. b. Internet is a necessary evil. c. ICT is one of the reasons for increasing cases of depression, divorce and violence in family relations. d. Social media is one of the major aspects of Online Reputation. e. Online reputation management is a very important task for an organization. f. Audio and visual editing technology has made the education sector more advanced. g. Digital signal is better than analog signal. h. All netizens do not follow the netiquette. 6. Answer the following questions in short. a. List the characteristics of good netizens. b. Write any four importance of digital reputation management. c. How has ICT eased the process of gaining education? Describe. d. Give examples of digital technology used in our daily life. Discuss the role of digital technology in the development of information and communication technology. e. Write any two advantages and disadvantages of digital technology in our daily life. f. ‘Digitalization has reduced the burden of carrying cash during buying and selling goods.’ Justify the statement.

342 infoRmation and communication tecHnology (ict) Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur g. How has the development of digital technology increased social crimes? Briefly explain. h. List the various activities of a person or a company that damages their Online Reputation. i. Write any four advantages and precautions of digital wellbeing. STEP3 7. Answer the following long questions a. Describe the factors that affect online reputation. b. Explain the relationship between netizens, netizenship and netiquette. c. What is digital wellbeing? Describe any three guidelines that a person must follow while surfing the internet. d. How do you record your audio from an android phone? Explain. e. Describe the negative aspects of digital technology. f. How does cutting and merging audio-visual files assist students in their academics? Describe. g. One of your relatives frequently uses the internet for advertising his school. But unfortunately, the fame of his school is declining. Now, answer the following questions based on the condition given. i. In terms of ICT, what name should be given to the relative? ii. What type of problem is he facing? State the problem. iii. Suggest to him or her a few steps uplift the fame of the school. h. Describe the various steps to be followed to cut and merge audio files. Also, write the significance of the cutting or merging process of audio-visual files. i. Your friend regularly uses the internet for various purposes. He randomly keeps opening websites without taking care of the cautions that pop out. Suggest to him a few internet etiquettes that he must follow while surfing on the internet. j. Based on the figure given alongside, answer the following questions. i. Name the type of signal represented by graphs A and B. ii. How is graph A different from graph B? iii. Which graph is discontinuous? Why? iv. Write the uses of graph B. (a) (b)

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 343 Key terms and terminologies of the unit 1. Classification of elements : The grouping of elements on the basis of their similarities and dissimilarities is called classification of elements. 2. Periodic Table : The table, or chart, which is obtained after arranging elements on the basis of similarities and dissimilarities is called the periodic table. 3. Mendeleev's periodic law : According to Mendeleev's periodic law, "The physical and chemical properties of elements are a periodic function of their atomic weights." 4. Mendeleev's periodic table:The table which is obtained after arranging elements on the basis of increasing atomic weight is called Mendeleev's periodic table." 5. Modern periodic law : Modern periodic law states that, "Physical and chemical properties of the elements are a periodic function of their atomic numbers." 6. Modern periodic table : The table which is obtained after arranging elements on the basis of increasing atomic numbers is called the Modern periodic table." 7. Isotopes : Isotopes are elements having the same atomic number but different atomic weights. 8. Lanthanides : The 15 elements from cerium (58Ce) to lutetium (71Lu) along with lanthanum (57La) are called Lanthanides. 9. Actinides : The 15 elements from thorium (90Th) to lawrencium (103Lr) along with actinium ( 89Ac) are called Actinides. 10. Periods : In the modern periodic table, there are seven horizontal rows, which are called periods. In a period, elements having gradual change in properties are placed one after another. Sequence of Curriculum Issued by CDC  Modern periodic law  Introduction to modern periodic table  Structure of modern periodic table, group and period  Sub-electronic configuration of the first 20 elements  s, p, d and f block elements of periodic elements  Position of metals, nonmetals and metalloids in the modern periodic table  Periodic variation (variation of atomic size, electro positivity, electro negativity, valency and reactivity) UNIT Classification of Elements 14 Estimated teaching periods Theory Practical 7 2 Dmitri Ivanovich Mendeleev is well known for his periodic table. He was born in Russian Empire on 8th February 1834 and died on 2nd February 1907. He was an inventor and a chemist. He formulated a periodic law based on atomic weight and arranged available elements in Mendeleev’s periodic table. He was honoured with the Davy medal, Faraday Lectureship Prize etc. D. I. Mendeleev About the Scientist

344 cl aSSification of elementS Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur 11. Groups : In the modern periodic table, there are a total of 18 vertical columns (IUPAC system), which are called groups. In a group, elements having similar properties are placed one below the other. 12. Sub-shell : Sub-shellls are the regions in main shells, where the probability of finding electron is maximum. 13. Aufbau principle : Aufbau principle states, "The filling of electrons always occurs from the sub-shells of lower energy level to the sub-shells of higher energy level. 14. s-Block elements : The elements whose last electron enters the s-orbital of the outermost shell are called s-Block elements. 15. p-Block elements: The elements whose last electron enters the p-orbital of the outermost shell are called p-Block elements. 16. d-Block elements : Elements whose last electron enters the d-orbital of the penultimate shell are called d-Block elements. 17. f-Block elements : Elements whose last electron enters the f-orbital of the ante-penultimate shell are called f-Block elements. 18. Atomic radius : Atomic radius is the distance between the outermost shell and the center of the nucleus of an atom. 19. Ionization energy : The amount of energy required to remove the outermost loosely bound electron of an isolated gaseous atom is called ionization energy. 20. Valence electrons : The electrons present in the outermost shell (or valence shell) of an atom are called valence electrons. 21. Valency : The total number of electron(s) gained, lost or shared by atoms during a chemical reaction is called valency. 22. Electronegativity : The amount of energy required for an atom to attract the outer electron of another atom is called electronegativity (EN). Introduction In the history of chemistry, grouping of elements into blocks, periods, and groups based on their properties is considered a big achievement. Previously very few elements were discovered. So, individual study of these elements was possible. With the development of science and human knowledge, many new elements were discovered. Thereafter, the study of an individual element became difficult. To make the study easy, fast and clear, chemists felt the need of grouping these elements. About 118 elements have been discovered till today and they have similarities as well as dissimilarities among one another. So, the grouping of elements on the basis of their similarities and dissimilarities is the called classification of elements. Many chemists have made attempts to classify the known elements. Among them Antoine Lavoisier was the first person who classified all the 32 known elements into metals and nonmetals. Since then many systematic classifications have been given by various scientists. Periodic Table The table, or chart, which is obtained after arranging elements on the basis of similarities and dissimilarities is called the periodic table. It is called the periodic table because elements having similar characteristics are repeated after a certain interval in the table. In the periodic table, there are horizontal rows, i.e., periods and vertical columns, i.e., groups.

Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Modern Concept Science & Technology - 10 345 Mendeleev's Periodic Law Russian chemist Dmitri Ivanovich Mendeleev studied the physical and chemical properties of 63 known elements and their compounds. After the study, he arranged all the known elements on the basis of increasing atomic weights. As a result, he found that elements with similar properties occur at regular intervals. On the basis of the above observation, Mendeleev formulated the periodic law in 1869 AD. According to Mendeleev's periodic law, "The physical and chemical properties of elements are a periodic function of their atomic weights." Periodic function means, if elements are arranged in the order of increasing atomic weights, the properties of the elements go on changing with their atomic weights. But after a certain interval, they repeat the properties of the previous elements and fall one below another in the same vertical column. Mendeleev's Periodic Table With the help of above mentioned periodic law, Mendeleev arranged elements according to increasing atomic weights. Hence, he found a table known as Mendeleev's periodic table. In Mendeleev's periodic table, elements are classified into horizontal rows called periods and vertical columns called groups. Elements with similar properties were in the same group and elements with gradual change in properties were in the same period. In Mendeleev's periodic table, the periods 4, 5 and 6 were divided into two halves to place more elements. Half of the elements were placed in the upper left corner and half of the elements were placed in the lower right corner of each box. Many elements were not discovered when Mendeleev formed the periodic table. So, he left some gaps for the undiscovered elements and proposed names for them, e.g., Eka–Boron, Eka–Aluminium, Eka–Silicon, Eka–Manganese, etc. Fig: A part of Mendeleev's periodic table

346 cl aSSification of elementS Approved by the Curriculum Development Centre, Sanothimi, Bhaktapur Merits of Mendeleev's periodic table 1. Mendeleev's periodic table was the first scientific and systematic study of all known 63 elements. 2. In Mendeleev's periodic table, there were many gaps for undiscovered elements. After their discovery, they got their proper place in the table. 3. Mendeleev's periodic table helped to correct the doubtful atomic weights of some elements on the basis of their position in the periodic table, e.g., gold (Au), platinum (Pt), uranium (U), etc. 4. With the help of Mendeleev's periodic table, properties of several elements were studied correctly. Demerits of Mendeleev's periodic table 1. Mendeleev could not arrange hydrogen properly because it shows the properties of both alkali metals and halogens. 2. Mendeleev could not arrange isotopes because they have different atomic weights but the same atomic number, e.g., 12 C⁶, 13 C⁶, 14 C⁶. 3. Mendeleev could not arrange Lanthanides and Actinides. 4. In Mendeleev's periodic table, some elements do not obey the periodic law. In some places, elements having more atomic weight were placed before those of less atomic weight. For example, 58.9Co 27 was placed before 58.6 Ni 28. 5. In Mendeleev's periodic table, more reactive alkali metals (Li, Na, K, etc.) and less reactive coinage metals (Cu, Ag, Au) were placed together in the same group. 6. The eighth group of Mendeleev's periodic table was not divided into sub-groups. 7. Inert gases or noble gases were absent. Modern Periodic Law A group of chemists led by Henry Moseley studied the chemical and physical properties of all known elements. They found that properties of elements depended more correctly on the atomic number than on atomic weight. Moseley said that atomic number is the fundamental property of the atom. Afterward, they proposed a new law called the modern periodic law. Modern periodic law states that, "Physical and chemical properties of the elements are a periodic function of their atomic numbers." Modern Periodic Table After the discovery of the modern periodic law, elements were arranged on the basis of increasing atomic numbers. As a result, they found that elements having similar properties fall one after another in the same vertical column called group. Elements having gradual change in the properties were in the horizontal row called period. Hence, a more correct table than Mendeleev's was obtained, which is known as the modern periodic table. So, "The table which is obtained after arranging elements on the basis of increasing atomic numbers is called the Modern Periodic Table." Correction of Defects of Mendeleev's Periodic Table by Modern Periodic Table In the Modern periodic table, elements have been arranged on the basis of increasing atomic numbers. As a result, all the defects of Mendeleev's periodic table were removed. The defects