Oasis School Science and Technology 10 New

Oasis School Science and Technology - 10 301 Fig. Alternative current Time Magnitude Fig. Direct current Time Magnitude Average voltage and frequency used in the mainline of Nepal Each country supplies predefined voltage, frequency and plug type for domestic and industrial use. However, a large region can use common standards. Many countries including the United States use 110 to 120 volts and 60-hertz frequency. Many other countries including Nepal use 230 volts and 50-hertz frequency. Magnetic effect of current When current is passed through a wire, it produces a magnetic field around it. This effect of an electric current is called magnetic effect. It was discovered by Hans Christian Oersted in 1820 AD. He found that a current carrying conductor was able to deflect a magnetic needle. Please note that a magnetic needle can be deflected only by a magnetic field. Therefore, a current flowing through a wire always gives rise to a magnetic field around it. Magnetic field around a wire Let us take a straight vertical wire AB which passes through a horizontal cardboard sheet C. The ends of the wire AB are connected to a battery. When the current is passed through the wire AB, it produces a magnetic field around it. The magnetic lines of force can be shown by sprinkling iron filings on the cardboard C. The iron filings arrange themselves in circles around the wire showing that the magnetic lines of force are circular in nature. Direction of magnetic field around a wire The tangent that is drawn on the circle gives the direction of the magnetic field. Direction of magnetic field depends upon the direction of the current. It can be explained by Maxwell's grip rule. Current carrying conductor N S Fig. Deflection of magnetic needle due to current carrying conductor Fig: Magnetic field around a straight current carrying conductor

302 Oasis School Science and Technology - 10 Maxwell's Right hand grip rule Maxwell's Right hand grip rule states that if a straight conductor carrying current is held in the right hand such that the thumb is pointed in the direction of the current, then the direction in which your fingers encircle the wire gives the direction of the magnetic lines of force around the straight wire. Fig: Direction of magnetic field around a straight current carrying conductor If the direction up current is reversed the direction of magnetic field will also be reversed. Magnetic field around a solenoid The coil of an insulated wire around a cylinder is called a solenoid. Whenever an electric current is passed through the coil magnetic field is produced in it. The magnetic field around a solenoid is identical to magnetic field around the bar magnet. One end of the solenoid gains north pole and another end gains south pole. If the direction of current is reversed the poles of magnetic field around solenoid will also be reversed. Magnetic field is uniform inside the coil, stronger at the poles and weaker at farther regions. Factors affecting the strength of a solenoid i. Total number of turns in the solenoid: By increasing the number of turns in the solenoid, the strength of an electromagnet is increased. ii. Current in the coil: If the current in the solenoid is increased, the strength of the solenoid increases. iii. Nature of core material: By using soft iron in the core of the solenoid, the strength of the electromagnet is increased. Solenoid is a temporary magnet. So, it is used to make electromagnet. Direction of the magnetic Field in a solenoid If we hold one end of the solenoid toward our eye and if the current is flowing in clockwise direction, then that end toward our eye will be south pole. Fig: Maxwell's Right hand grip rule Fig: Magnetic field around a solenoid

Oasis School Science and Technology - 10 303 If we hold one end of the solenoid toward our eye and if the current is flowing anticlockwise direction, then the end toward our eye will be north pole. It can be explained by Maxwell’s right hand grip rule in solenoid. Maxwell's right hand grip rule for solenoid According to the Maxwell's right hand grip rule for solenoid " If we grip the solenoid with our right hand so that fingers wraps the solenoid and the thumb is stretched out, then if the current is flowing in the direction of wrapped fingers then the thumb represents the direction of north pole. Magnetic Flux The magnet has north pole and south pole. Outside the magnet, the unit north pole travels from the north to the south in a curved path. The imaginary curved path in which unit north pole travels from the north to the south pole is called magnetic lines of force. A stronger magnet produces more number of magnetic lines of force. The region up to where magnetic lines of force of a magnet reaches is called its magnetic field. The direction of magnetic field is from south to north pole of a magnet within the magnet and the field lines will go from north to south outside of the magnet. Magnetic field is a vector quantity. The magnetic lines of force never intersect each other. They are crowded at north pole and south pole. They are spread thin away from the magnet and at the middle of magnet. So magnetic field is stronger at poles but weaker at middle part and away from the magnet. Fig: magnetic fields around a bar magnet, solenoid, earth and current carrying straight conductor. When a conductor is placed in a magnetic fields, certain number of magnetic lines of force pass through the conductor. The number of magnetic lines of force passing through a certain area of a conductor held perpendicularly is called magnetic flux. It is usually donated by phi (Φ). The device that measures magnetic flux is called flux meter. The flux meters get higher reading when placed near the poles but gets low reading at the middle parts or away from the magnet. The SI unit of magnetic flux is Weber (Wb) named after Wilhelm Eduard Weber. The CGS unit of magnetic flux is Maxwell. In given figure, Conductor AB is placed in a magnetic field. Few magnetic lines of forces are passing through it. Total number of magnetic lines of forces passing through the surface of the conductor AB is called its magnetic flux. Fig: Maxwell's right hand grip rule to show direction of magnetic north pole in a solenoid

304 Oasis School Science and Technology - 10 Motor Effect A current carrying wire exerts a force on a magnetic compass and deflects it from its usual north-south position. So, a current carrying conductor exerts mechanical force on a magnet if the magnet is free to move. The force can produce a motion in the magnet. The reverse of this is also true, i.e., a magnet exerts a mechanical force on a current carrying wire if the wire is free to move. This force can produce a motion in the wire. This result can be obtained by applying Newton’s third law of motion. If a current carrying conductor exerts a force on a magnet, the magnet will exert an equal and opposite force on the current carrying conductor. In 1821 AD, Michael Faraday discovered that when a current carrying conductor is placed perpendicular to the magnetic field, the conductor moves. This effect is called motor effect. When current is passed through a conductor, a magnetic field is developed around it. Attraction and repulsion occur between the magnetic field of a magnet and that of the current carrying conductor. As a result, the wire moves. Reasonable Fact Kinetic energy is produced on an electric motor when we pass electricity in the conductor which is placed inside a magnetic field. Kinetic energy is produced on an electric motor when we pass electricity in the conductor which is placed inside a magnetic field because the magnetic field produced on the conductor is deflected by the permanent magnetic field of the motor. Activity 1 Find small electric motors or buy a new one and use it to make a model of an electric fan. Activity 2 1. Take a conductor and a conducting wire. 2. Make a support of the conducting wire at two points 'A' and 'B'. 3. Hang the conductor on a stand as shown in the given figure and connect the two terminals of the conductor with a battery. 4. Bring a U- shaped magnet close to the conductor. Do you observe a movement of the conductor? The motion of the conductor is due to the motor effect. Fig. Motor effect Conducting wire N S Magnetic lines of force Motion Current Fact File Motor effects is impossible without magnets.

Oasis School Science and Technology - 10 305 Electric Motor An electric motor is a device which converts electrical energy into mechanical energy. Every motor has a spindle which rotates continuously when the current is passed through it. An electric motor works on the principle of motor effect. Structure of electric motor The electric motor is a load. It contains a powerful magnetic field. An armature is kept inside the magnetic field. When electricity is passed into the conductor, a magnetic field is produced in the armature. There will be two magnetic fields in the electric motor. Two magnetic fields repel each other and starts to rotate. Fig. Internal structure of an electric motor Fact File It is to be noted that when current is passed through a generator, or dynamo, it becomes an electric motor. So, an electrical generator can be run "backwards" to form a motor. Fact File An electric motor works on the principle that, when a rectangular coil is placed in a magnetic field and current is passed through it, a torque (i.e., a twisting force that causes machinery to rotate) acts on the coil, which rotates it continuously. Fig. Electric motor Fig: schematic diagram of electric motor

306 Oasis School Science and Technology - 10 Application of motor effect in our daily life Some of the useful aspects of motor effects are discussed below: i. Electric motors are used in a washing machine. ii. Electric cars, hair dryers and CD players also work on motor effects. iii. The electrical appliances such as blenders, grinders and electric fans are based on m o t o r effects. iv. Construction tools such as electric drills, electric saws and air conditioner has electric motors. v. Electric flour mill, water pump and lift also work with an electric motor. Fig: electric fan Fig: drill Fig: blender Fig: some application of electric motor Reasonable Fact Kinetic energy is produced on an electric motor when we pass electricity in the conductor which is placed inside a magnetic field. Kinetic energy is produced on an electric motor when we pass electricity in the conductor which is placed inside a magnetic field because the magnetic field produced on the conductor is deflected by the permanent magnetic field of the motor. Activity 3 Find small electric motors or buy a new one and use it to make a model of an electric fan. Electromagnetic Induction You have seen that an electric current can produce a magnetic effect as in an electromagnet. Is the reverse situation possible? Fig. (b) Electromagnetic induction Conductor Galvanometer A S N B Galvanometer Coil Magnet Fig. (a) Fact File Motor effects is impossible without magnets.

Oasis School Science and Technology - 10 307 Figure (a) shows an experiment conducted by Michael Faraday. In this experiment, a coil of conducting wire is connected to the galvanometer. A galvanometer is a device which is used to detect current. In this instrument, the zero is at the centre of the scale, so the current can be measured in either directions. When a strong bar magnet is moved back and forth in and out of the coil, the galvanometer needle shows deflection due to induction of current in the coil. This experiment helped Faraday to put forward his theory of electromagnetic induction, which finds innumerable applications today. The process of inducing current in a closed coil due to the relative motion between the magnet and the coil is called electromagnetic induction. Faraday's Laws of Electromagnetic Induction Depending on above experiments, Michael Faraday has given the laws of electromagnetic induction in 1831 AD which are as follows: i. Whenever magnetic flux linking a coil or a conduction changes, an emf is induced in it. ii. The magnitude of induced emf is directly proportional to the rate of change of magnetic flux. i.e. induced emf = change in magnetic flux x time taken iii. The induced emf in the coil lasts as long as the change of magnetic flux linking the coil continues. Activity 4 Take a match box. Make many turns of an insulated copper wire around it as shown in the figure. Connect the galvanometer with the two ends of the wire. Move a bar magnet in and out of the box. Is there any deflection in the galvanometer? Yes, there is deflection in the galvanometer due to the electromagnetic induction. The needle of the galvanometer deflects in the opposite direction as before and after the magnetic motion in and out of the box. Fig. Electromagnetic induction Galvanometer Turns of wire Match box Magnet S Reasonable Fact A stationary magnet does not induce a current in a coil. In case of a stationary magnet, the magnetic lines of force connected to the closed circuit or a coil does not change. When it is moved to and fro, the magnetic lines of force intersected by the circuit changes and e.m.f. gets induced. So, a stationary magnet does not induce a current in a coil. Fact File The voltaic cells were used for electricity in 1800 AD. Michael Faraday discovered electromagnetic induction in 1831.

308 Oasis School Science and Technology - 10 Generator and Dynamo A generator, or dynamo, is a device which converts mechanical energy (or kinetic energy) into electrical energy. It works on the principle of electromagnetic induction, i.e., when a straight conductor is moved perpendicular to the magnetic field, current is induced in the conductor. A generator produces current on a large scale whereas a dynamo does it on a small scale. Bicycle Dynamo A dynamo is used in a bicycle to produce current to light a bulb. It works on the principle of electromagnetic induction, i.e., when a conductor is moved perpendicular to the magnetic field, current is induced in the coil. A dynamo has a permanent magnet which moves near to a closed coil. Due to the motion, the magnetic flux linked to the coil changes. As a result, current is induced in the coil. An armature is connected to a tyre of a bicycle to rotate the magnet. The current is induced in the bicycle dynamo so long as there is motion in the tyre. Activity 5 Connect the rotating end of the dynamo to the tyre of a bicycle and rotate the tyre at variable speed. Observe the brightness of the bulb by increasing and decreasing the speed. What do you observe? Reasonable Fact The brightness of the bicycle dynamo bulb increases when the speed of the bicycle increases. When the speed of the bicycle increases, the number of magnetic lines of force intersected by the coil in the bicycle dynamo increases. It increases rate of change of magnetic flux which increases the magnitude of induced current and brightness of the bulb. Generator In a generator, a strong and powerful electromagnet is used. When the turbine is rotated by external force, the rotor fixed to the magnet will also rotate. As a result, current is induced in the coil due to the change in the magnetic flux linked to the coil. The magnitude of current induced by a generator, or dynamo, can be increased by the following methods: i. By increasing the number of turns in the coil ii. By increasing the speed of the rotation iii. By decreasing the distance between the magnet and the coil iv. By increasing the strength of the magnetic field by using a powerful magnet. AC Generator and DC generator are two types of generators based on the polarity of current they produce. Fig: Bicycle dynamo Fig. Generator

Oasis School Science and Technology - 10 309 AC Generator AC generator is commonly used to run industries and various domestic appliances. It is also called alternators. It is based on electromagnetic induction. Structure of a AC Generator Powerful electromagnets are present in the AC generator to generate powerful magnetic fields around the coil. The conducting coil inside the magnetic field is called armature. It is made of soft iron core to increase the rate of production of current. There are two slip rings in AC generator each at one end of the armature. Whenever the armature rotates current will be induced in it. When armature rotates half turn current is collected by first slip ring. When armature rotates another half turn current changes direction and it is collected by second slip ring. So the direction of induced current keeps changing. The carbon brushes are in contact with slip rings. They collect electricity from slip rings. Total number of complete rotations made by armature per second is called frequency. AC generators are used in hydro power stations, wind farms and thermal power stations. Each country supplies predefined voltage, frequency and plug type for domestic and industrial use. However, a large region can use common standards. Many countries including the United States use 110 to 120 volts and 60-hertz frequency. Many other countries including Nepal use 220 volts to 240 volts and 50-hertz frequency. Frequency of AC can be controlled by controlling the rotation of the turbine. If the turbine of generator rotates 3000 times per minutes (50 times per second), it can produce current of frequency of 50Hz. Voltage is directly proportional to frequency. If rate of rotation of armature is increased, frequency and voltage will increase. Fig: AC generator Fact File In previous centuries most electrical devices used DC, so the commutators (set of rotating switch on armature of generator) were used in generator so that it can convert AC into DC for domestic uses. Those DC generators were then called dynamos. v v T + cycle O -cycle Fig: Voltage-time graph for AC

310 Oasis School Science and Technology - 10 Differences between a Dynamo (generator) and an Electric motor S.N. Dynamo (generator) S.N. Electric motor 1. It is a device which converts mechanical energy into electrical energy. 1. It is a device which converts electrical energy into mechanical energy. 2. It works on the principle of Faraday’s laws of electromagnetic induction. 2. It works on the principle of motor effect. 3. Direction of current can be found by using Fleming’s right hand rule. 3. Direction of motion of conductor can be found by using Fleming’s left hand rule. Hydroelectricity The electricity produced when turbine of generator is rotated by the flowing water is called hydroelectricity. It is clean and renewable source of energy. The hydroelectric power plant contains a reservoir (forebay), tunnel (penstock), turbines and generators. Huge reservoirs are made in suitable area. Large quantity of water is collected in it. Water stored in a dam has huge quantity of potential energy. The water from the dam is passed through the tunnel downhill. The kinetic energy gained by running water rotates the turbine. The turbines are connected to the generators. When the armature of generator rotates inside the powerful magnetic fields, there will be change in magnetic flux and current will be produced. Advantages of Hydropower i. It is a renewable source of energy. So, it will never get depleted. ii. It is a pollution free source of energy. iii. It is cheaper in the long term although the initial cost is high. iv. It is widely used in electric and electronic devices, like computers, television sets, bulbs, CFL, etc. Solved Question 1 Write two reasons why higher priority is given to the production of hydroelectricity in Nepal. Two reasons for giving higher priority in Nepal for the production of hydroelectricity are: i. Hydropower is the most potential source of energy in Nepal. Nepal is the Fact File Hydropower is the most potential source of energy in Nepal. Our country is the second richest country after Brazil in hydroelectric power potential due to its flowing water in many rivers. The estimated hydroelectricity generation capacity of Nepal is about 83000 MW. Fig: technology of hydroelectricity

Oasis School Science and Technology - 10 311 second richest country after Brazil in hydroelectric power potential due to its many rivers. ii. Hydroelectricity is cheaper in the long term. It is a renewable and pollution free source of energy. Solved Question 2 Give two reasons to justify that the use of hydroelectricity should be increased more than that of fossil fuel energy. Two reasons to justify that the use of hydroelectricity should be increased more than that of fossil fuel energy: i. Hydroelectricity is a pollution-free source of energy, while fossil fuel causes air pollution when used. ii. It is a renewable source of energy. Wind Energy Moving air is called wind. It has kinetic energy. This energy is utilized for rotating wind mills to generate electricity. The energy produced by the fast-moving wind is called wind energy. The sun is responsible for the generation of this form of energy as it governs the movement of air in the atmosphere. Wind energy is used to rotate turbines to generate electricity. Human beings have been using wind as a source of energy for ages. In the olden days, it was used for sailing, pumping water, removing husk from the grains and for grinding grains or milling. Wind energy is outcome of solar energy. Advantages of wind energy. i. Wind is a renewable source of energy, we never run out of it. ii. It is a clean source of energy. It does not cause pollution. iii. It is free of the cost and is reliable. iv. Wind farms can be built off-shore. Thermal Energy The energy produced from the temperature of the heated substance is called thermal energy. A thermal power station can use thermal energy to produce electricity. The main concept of thermal power stations is to use heat energy to convert water into steam and use the pressurised steam to rotate a steam turbine which will eventually produce electricity. Any source of heat can be used to convert water into pressurised steam. For examples fossil fuel, nuclear energy, geothermal energy, biofuel, solar energy and waste incineration. The design of a thermal power plant varies based on the source of heat. The thermal power plant is bad for the environment because it emits lots of greenhouse gases into the environment. Fact File Nowadays, wind mills are operated by wind energy to generate electrical and mechanical energy. Investigations have revealed that a minimum velocity of 15 km/h is required to keep a wind mill operational. Fig. Wind farm in Nepal Figure of thermal power plant

312 Oasis School Science and Technology - 10 Working mechanism of thermal power plant A coal-powered thermal power station burns coal to generate electricity. The coal is pulverised and burned in a pulverised coal-fired boiler. The heat converts water into very hot steam. The pressurized fast flowing steam is passed into the turbine. The turbine rotates to produce electricity. Advantages of thermal energy i. It is a cheaper source of electricity. ii. Coal is cheap and easily available to produce thermal energy. iii. It can use geothermal energy, solar energy or waste incineration also to produce thermal energy. iv. It costs less to make a thermal power plant. Reasonable Fact Thermal power plants should be discouraged. Thermal power plants should be discouraged because it is one of the major sources of air pollution, global warming and climate change. Activity 6 Make a 3D model of a thermal power plant. Transformer A transformer is a device that converts high voltage AC to low voltage AC of the same frequency and vice versa. It works on the principle of mutual induction, i.e., whenever the current (magnetic flux) through a coil changes, an e.m.f. is induced in the neighbouring coil. According to this principle, when the electric current in a closed circuit (primary coil) changes polarity, the alternating current (AC) creates a alternating magnetic field. A second circuit (secondary coil) within this magnetic field will experience this change in the magnetic field. There will be change in magnetic flux. Therefore, an electromotive force is set up in the second circuit (secondary coil) called induced e.m.f. (or transformer emf) due to magnetic flux linkage. If the two ends of the secondary coil are connected through an electrical load, current will flow. A transformer is widely used in electric and electronic devices, such as the radio, TV, trolley bus, factories, computers, etc. Structure of a transformer A transformer consists of two separate coils winding on a laminated iron core. The two coils are called primary coil and secondary coil. The coil of the transformer in which AC voltage is given is called primary coil and the coil from which AC voltage is taken is called secondary coil. The iron core, when used in a single block, develops eddy current, and the core is heated up. The heat so produced damages the internal Fact File There are about 8,500 coal-fired power stations worldwide totalling over 2,000 gigawatt. Fig. Transformer Fig. Structure of a transformer A.C. input A.C. output Iron core Secondary Coil Primary Coil Magnetic field in core

Oasis School Science and Technology - 10 313 insulation besides causing loss of energy. In order to minimize the heating effect, thin insulated metal sheets are adjusted to make the core of a transformer. These iron sheets are coated with insulating materials like varnish or shellac. This process is called lamination. The core of a transformer is laminated to minimize energy loss due to the production of eddy current. Working Principle Alternating current passes through the primary coil when it is connected to an AC source. The magnetic field due to AC in primary coil changes in both magnitude and direction. This changing magnetic field changes the magnetic lines of force linked with the secondary coil. According to the Faraday's laws of electromagnetic induction, whenever the magnetic lines of force linked with a closed circuit changes, an emf gets induced from two terminals of the secondary coil. Thus, a transformer is based on the principle of mutual induction. The principle of mutual induction states that "an emf gets induced in a coil by passing an alternating current in the neighbouring coil." Primary voltage (V1 ) and Secondary voltage (V2 ) The input voltage of a transformer is called primary voltage (V1 ) and the output voltage is called secondary voltage (V2 ). The number of turns in the secondary coil (n2 ) can be calculated by the following relation: Secondary Voltage V imary Voltage V ( ) Number of turnsin o Pr ( ) sec 2 1 = ndary coil n Number of turnsin primary coil n V V n n ( ) ( ) 2 1 2 1 2 1 ∴ = By the appropriate selection of the number of turns, a transformer thus allows an alternating voltage to be stepped up or stepped down. A transformer is based on the following two laws: 1. In a transformer, the input power (I1 V1 ) is equal to the output power (I2 V2 ), where I1 = input current, V1 = input voltage, I2 = output current and V2 = output voltage. 2. The magnitude of the induced e.m.f. is directly proportional to the ratio of the number of turns in the secondary coil to the number of turns in the primary coil. Types of Transformer There are two types of transformers: step up transformer and step down transformer. a. Step up transformer: The transformer which converts low voltage AC to high voltage AC is called a step up transformer. Such a transformer has more number of turns in the secondary coil than in the primary coil, i.e., n2 > n1 . It is used in electric grids to save electrical energy during power transmission through overhead wires. It is also used in television sets, refrigerators, etc. and for producing X-rays in X-ray tubes. Output Input AC source 220V 11000V Fig. Step up transformer

314 Oasis School Science and Technology - 10 b. Step down transformer: The transformer which converts high voltage AC to low voltage AC is called a step down transformer. Such transformers have less number of turns in the secondary coil than in the primary coil, i.e., n2 < n1 . It is used in radios, cassette players, TV sets, etc. It is also used at power substations to step down the voltage before its distribution to consumers. Fact File In a transformer, the input energy and output energy are equal. The voltage is directly proportional to the ratio of number of turns. A transformer cannot change the e.m.f. of a dry cell because the magnitude of the DC does not change. Activity 7 Open the outer cover of a step down transformer which is not in use and find out its working principle and structure. Differences between Step up transformer and Step down transformer S.N. Step up transformer S.N. Step down transformer 1. It converts low voltage AC into high voltage AC. 1. It converts high voltage AC into low voltage AC. 2. The number of turns in the secondary coil is more than that in the primary coil. 2. The number of turns in the secondary coil is less than that in the primary coil. 3. It is used in power transmission lines to increase voltage. 3. It is mostly used in household devices which run at less than 220V. Worked out Numerical 1 Calculate the number of turns in the secondary coil if a transformer is connected to the AC main of 220V to produce 12V with the primary coil of 1000 turns. Also, write down the type of the transformer. Solution: Given, Primary voltage (V1 ) = 220 V No. of turns in the primary coil (n1 ) = 1000 Secondary voltage (V2 ) = 12 V No. of turns in the secondary coil (n2 ) = ? We know, Fig. Step down transformer AC source Input 11000V Output 220V

Oasis School Science and Technology - 10 315 V V n n or n V n V 2 1 2 1 2 2 1 1 12 1000 220 54 5 = = × = × = , . ≈ 55 turns Hence, the number of turns in the secondary coil is 55. The type of transformer is step down because secondary voltage is less than the primary voltage. Worked out Numerical 2 The number of turns in the secondary coil is 150 times less than that in the primary coil. If the secondary voltage is 220V, calculate the primary voltage. Solution: Given, Secondary voltage (V2 ) = 220V Primary voltage (V1 ) = ? Let the number of turns in the secondary coil (n2 ) be x Then number of turns in the primary coil (n1 ) is 150x We know, ∴ Primary voltage = 33000 V. Worked out Numerical 3 The number of turns in the primary coil of a transformer is double that of the secondary coil. Calculate the input voltage if 220V is generated by the secondary coil. Solution: Given, Let the number of secondary coil (n2 ) be x Then the number of primary coil (n1 ) be 2x Input voltage (V1 ) = ? Output voltage (V2 ) = 220 V V1 n1 = V2 n2 V V n n or V V n n x x V 2 1 2 1 1 2 1 2 220 150 33000 = = = × =

316 Oasis School Science and Technology - 10 or, V1 = V2n1 n2 = 220 × 2x x = 440 ∴ The input voltage (V1 ) = 440 V. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. 230 volts of electricity is supplied in the main lines of Nepal but mobile devices can intake around 5 volts of current only. Which electrical device does the charger contain? What does it do? Even though 230 volts of electricity is present in the main lines of Nepal we can easily charge mobile devices that only need around 5 volts. The mobile device won’t be damaged because of the charger. The charger contains an adapter which contains a stepdown transformer. The step-down transformer converts high AC voltage into low AC voltage. It is appropriate voltage for mobile devices. 2. 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 anticlock wise. 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, which is clock wise. Faraday’s laws of electromagnetic induction are being tested in this experiment. 3. Ashmita uses bicycles to go to school. She has installed a dynamo on her bicycle so that she can ride the bicycle at dusk. 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. 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. So, when she pedalled faster, the permanent magnet of the dynamo also rotated faster. Since the magnet is inside the coil, the rate of change of magnetic flux also increased. As a result, higher emf was produced and the bulb glowed brighter. 4. The topography of Nepal supports 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

Oasis School Science and Technology - 10 317 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. 5. Thermal energy power plant is not a viable source of energy for Nepal. A thermal energy power plant runs coal or any other organic materials to run a steam boiler. It can rotate a turbine to produce hydroelectricity. In the case of Nepal, we do not have a sufficient source of coal. So thermal power plants cannot be operated in Nepal. It will be very expensive to use it as a source of electricity because we have to import coal from abroad. Therefore, thermal energy powerplant is not a viable source of energy for Nepal. 6. An electric motor and an electric generator are two sides of the same coin from the construction point of view. In the generator, the turbine is rotated to produce electricity. In an electric motor, electricity is passed into the turbine so that it can rotate. Even though their function is different, their structure is basically the same. The generator has a conducting rod inside a magnetic field. An electric motor also has a conducting rod inside a magnetic field. They have almost the same construction. Therefore, electric motors and electric generators are two sides of the same coin from the construction point of view. 7. 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? The alternating current generated in hydropower stations is 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 called 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 these devices. 8. Study the given diagram and answer the following questions. i. Name the device and the principle it is based on. The device shown in the diagram is an AC generator. It is based on electromagnetic induction. ii. Which rule helps to find the direction of current produced by this generator? Fleming's right-hand rule helps to find the direction of the current produced by this generator.

318 Oasis School Science and Technology - 10 iii. What happens if the turbine is rotated faster? If the turbine is rotated faster higher magnitude of emf and current is produced. iv. What type of magnets are used in these devices? Electromagnets are used in these devices. v. Why are powerful magnets used in these devices? Powerful magnets are used in generators so that a greater magnitude of the current can be produced. Exercises 1. Choose the best answer from the given alternatives. a. Frequency of AC is 50 Hz in Nepal. What does it mean? i. Hydroelectricity changes polarity 50 times per second in Nepal. ii. 50 ampere of electricity is supplied per second. iii. Voltage of current supplied in Nepal is 50 volts. iv. 50 coulomb of electricity flows per second b. A magnetic compass deflects when brought closer to the current-carrying conductor. Why? i. it is attracted by the copper ii. it is repelled by the copper iii. it is responding to terrestrial magnetism iv. it is responding to the magnetic field formed by the flowing current c. Why is no current induced as soon as the turbine stops in the generator? i. there is no potential difference ii. magnetic field becomes weaker iii. there is no change in magnetic flux iv. the magnet loses its power d. Transformer with an equal number of primary and secondary turning is useless. Why? i. It has an equal number of primary and secondary turnings. ii. it will waste electricity. iii. it cannot change the voltage of alternating current iv. it does not have a soft iron core e. Which effect is shown in the diagram? i. electromagnetic induction ii. motor effect iii. magnetic effect of current iv. mutual induction f. How can we increase the magnitude of the current produced bythe dynamo? i. use powerful electromagnets ii. supply higher voltage of a current iii. use powerful permanent magnets iv. use loadstones

Oasis School Science and Technology - 10 319 2. Define the following terms with required examples. a. Alternating current b. Direct current c. Magnetic effect of current d. Magnetic flux e. Electromagnetic induction f. Maxwell’s grip rule g. Generator h. Dynamo i. Motor effect j. Electric motor k. Hydroelectricity l. Wind energy m. Transformer n. Mutual induction o. Step up transformer p. Step down transformer q. Solenoid 3. Answer the following questions in very short. a. Who discovered the magnetic effect of electricity? b. Which principle is dynamo based on? c. What is the direction of the magnetic field when current flows upward in a straight conductor? d. What is the energy produced by the turbine rotated by the river called? e. Which electrical device can alter the voltage of the AC? f. What principle the transformer is based on? g. The transformer has two times the primary turnings than the secondary one? What type is it? h. Name the type of transformer which is used to play radio with 12 volts in the electric line of 240 volts. i. Which type of current does not have frequency and which one has? j. Write the mathematical equation for a transformer. 4. Give reasons. a. The bulb does not glow in an open circuit but glows in a closed circuit. b. Voltage of DC cannot be altered by a transformer. c. A magnetic compass deflects near the conducting wire in a closed circuit. d. Generator is a source of electricity. e. Dynamo can produce more electricity if the bicycle runs faster. f. When electricity is passed in the conductor placed inside a magnetic field, it rotates. g. Hydroelectricity is the best alternative source of energy for Nepal. h. Nepal should install a wind farm in mountainous regions. i. Alternating current would be useless without a transformer. j. Air conditioner does not operate on DC. k. When a magnetic compass is placed near a conducting wire, its needle will deflect. l . Transformer is useless if the primary coil and secondary coil have equal windings. 5. Differentiate between the following. a. Alternating current and direct current b. Generator and dynamo c. Electric motor and generator d. Motor effect and electromagnetic induction

320 Oasis School Science and Technology - 10 e. Hydroelectricity and wind energy f. Step-up transformer and step-down transformer 6. Answer the following questions in short. a. Describe the magnetic field around the straight current-carrying conductor. b. Draw the diagram of step-up transformer and label the coils. c. What are the advantages of hydroelectricity? d. Write any two ways of increasing the strength of solenoid. e. Give two examples of AC source and DC source each. f. Describe Maxwell’s grip rule with a diagram. g. What is used to laminate the core of the transformer and why? h. Frequency of electricity in Nepal is 50 Hz. What does it mean? i. Draw the current-time graph of AC and DC. j. Draw the diagram to show the magnetic field around a solenoid. Use Maxwell's grip rule to explain the direction of the magnetic field. k. Write Faraday’s laws of electromagnetic induction. 7. Draw a neat figure showing the structure of a transformer which is used to play a radio. Name the type of transformer shown in the given figure. Calculate the secondary voltage of this transformer. (Ans: 222.22V) 1000V 450 turns 11000V Output=? 100 turns 8. Answer the following long questions. a. What are Faraday’s laws of electromagnetic induction? b. Describe the structure of the dynamo. c. What can be done to increase the magnitude of induced current from a generator? d. Describe the motor effect with a suitable diagram. e. What is a hydropower station? What type of electricity is produced by them? How is hydroelectricity produced? What kind of transformer is used in the main hydropower station, sub-power station and domestic tools? How is electricity transferred from the powerhouse to the consumer? f. Describe the structure of the transformer with the help of a neat and clean diagram. g. Describe the step-down transformer with the help of its diagram. Mention its uses. h. Describe the step-up transformer with the help of its diagram. Mention its uses. i. Current supplied in Nepal is around 220 V to 240 volts. However, many electronic devices that run at lower voltages are used in our daily life. How does the transformer help us to use these devices? Explain.

Oasis School Science and Technology - 10 321 9. Study the given diagram and answer the following question. i. What happens in the needle of the galvanometer when magnet is inserted inside the coil? ii. What happens in the needle 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? b. Study the given diagram and answer the following questions. i. Name the device. ii. What is the reason for the production of motion in the conductor? iii. What is the name of the phenomenon that produces motion in a conductor? iv. What can be done to increase the rate of rotation? 10. Numerical a. The number of turns in the primary winding of a certain transformer is 150 times more than that in the secondary winding. Calculate the input e.m.f in the primary winding if the e.m.f generated in the secondary winding is 220V AC. [Ans: Rs. 409.09 turns] b. The power supply to the primary coil of a transformer is 220 V and the turns in the primary coil are 1000. What must be the number of turns in the secondary coil to run a radio of 8 V from this transformer? c. In a transformer, the ratio of secondary turns to primary turns is 3:1. Which type of transformer is it? Find the secondary voltage when the transformer is connected to a power supply of 220 V. d. A step-up transformer has 500 turns on its secondary coil and 50 turns on its primary coil. An alternating current of 16 A flows in the primary coil when it is connected to a 12 V AC supply. Calculate: i. The power input to the transformer ii. Output voltage from the secondary coil e. A mobile is being charged with the adapter of 12 V. It is connected to 220 volts. If there are 1000 primary turns find the secondary turns?

322 Oasis School Science and Technology - 10 UNIT 12 UNIVERSE Estimated teaching periods Theory 4 Practical 1 • 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) The Sequence of Curriculum Issued by CDC 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. About the Scientist Georges Lemaitre Key terms and terminologies 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. 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

Oasis School Science and Technology - 10 323 space and time do not exist anymore is called the close universe. 9. Big crunch : The hypothesis in which every single matter comes closer and condenses into an infinitely dense and hot singularity if the gravitation is far greater than expansion force is called big crunch. 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 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. The word universe comes from two words: "uni," which means "one," and "versus," which means "turned into." The Universe is a very big secret. It is because science doesn't fully understand the most basic things, like the shape, size, origin, and growth. Astronomy is the branch of science that studies the universe. Similarly, astrophysics is a branch of physics that studies the physical nature, laws, and principles of astronomical objects and events in the universe. The main reason that the universe exists is gravitational force. Importance of gravitational force in the universe i. Formation of star The cloud of hydrogen gas in space is known as a nebula. They are compressed into a huge ball of gas by gravitational pull. It eventually builds up enough pressure and temperature to begin a thermonuclear fusion reaction after it compresses due to its own gravity. First, a protostar will be formed which will later change into a star. ii. Formation of the solar system The solar system is formed when nearby celestial bodies are attracted together by the gravitational pulling force of the sun during its formation. Due to the gravity of the sun, various objects, including planets, asteroids, comets, and dwarf planets, orbit (revolve) around it. The gravitational attraction of the planets attract satellites around them. The planets are circled by satellites due to gravitational force. Fig: formation of star from the nebula Fig: formation of solar system

324 Oasis School Science and Technology - 10 iii. Formation of the galaxy Black holes are the remains of massive dead stars. Their gravity and density are extremely large. The gravitational pull coming out from the black holes is observed throughout the galaxy and beyond the galaxy. The stars are attracted together by gravitational force to form a galaxy. Hundreds of billions of stars are attracted by the gravitational pull of black holes, creating a huge galaxy in the universe. For example; we live in a spiral galaxy called the Milky Way galaxy which 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 1 lakh light years. This galaxy is formed because of the gravitation among the black hole Sagittarius-A and billions of stars being pulled toward it. iv. Formation of atmosphere around the earth The atmosphere is the layer of air that surrounds the Earth. The air of the atmosphere is a matter. It has mass. So, gravitation exists between the earth and the atmosphere. Gravity binds air around the earth. Hence, the atmosphere is formed. Reasonable Fact 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. The 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 Fact File Gravity is the weakest force in the universe. Even lifting a book is work against gravity.

Oasis School Science and Technology - 10 325 Study of the Universe Big bang theory The universe appears to be expanding as seen through Hubble's telescope. It was the result of a massive explosion. The origin of the universe is then imagined based on this observation. The big bang theory is the name given to this hypothesis. Big bang theory is the explanation for how the universe began by expanding from a state of high density and temperature. The big bang theory was proposed by Georges Lemaitre in the 1920s. 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. The big bang theory says that the big bang made 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 contracted state of an atom. Due to high pressure and high energy, the atom exploded(big bang) producing universe. The result of big bang Due to the big bang, all the heavenly bodies like stars, planets, comets, asteroids, meteors, etc. were created. The galaxies are moving apart increasing the size of the universe. As a result of 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. Reasonable Fact There were 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 on chart paper to show how the universe came to be, from the big bang to the way it is now. Post it in the classroom. Hubble Study There was a very big telescope called Hubble's telescope. It was sent into space on April 24, 1990. It takes clear pictures of space, planets, stars, and galaxies. It discovered the Fig. big bang

326 Oasis School Science and Technology - 10 age of the universe, black holes, the distance of galaxies from Earth, etc. Over one million observations made by Hubble shows the universe is expanding and speeding up. A big bang indicates an explosion. As a result, things should shift away from the explosion. Based on Hubble's observations, it is concluded that galaxies are expanding and accelerating. The smaller heavenly bodies are also very far away from the Earth. They have more speed. Hubble Law Hubble 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 (kilometer per second per Mega parsec). Explanation of Hubble law Hubble equation 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. We knew that, the universe is expanding, light from some galaxies will never reach us because it has already traveled a long distance. We can see only a portion of the universe. The observable universe is the visible part of the universe from Earth. Reasonable Fact 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. The Fate of the Universe The universe is expanding, as observed by Hubble's telescope. Will it continue to expand forever, or will it stop expanding and condense? What will happen to the universe in the Fig. graph plotted by Hubble's study

Oasis School Science and Technology - 10 327 end? These are some of the questions that come to mind. Many scientists have proposed various theories about the fate of the universe. The close universe, open universe, and flat universe hypotheses are the most authentic. These models of universe are based on the magnitude of gravitational force, energy from the big bang, and dark energy. The gravitational force attracts heavenly objects. It is called centripetal force. Whereas the energy from the big bang and the pushing force from critical density repels heavenly objects. It is called centrifugal force. i) 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. ii) 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. iii) 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 Suppose the universe is expanding as seen through Hubble's telescope. However, we have discovered that the gravitational forces of black holes are strong enough to pull billions of stars together to form galaxies. These stars are hold up within the gravitational field of the black holes and cannot escape. What if the mean density of universe is greater than critical density and there are enough masses in the universe that can generate enough gravity to counteract the acceleration generated by the big bang and 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 closer 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 Fact File 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. Fig: close universe Fig: open universe Fig: flat universe Fact File If mean density of the universe is more than critical density then the universe collapses into a point called close universe.

328 Oasis School Science and Technology - 10 universe is oscillating (Big bounce). It means the big crunch and big bang occur alternately. Therefore, the universe is said to be the closer 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. Reasonable Fact 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 3 Discuss the idea of a closed universe with your friends and teacher. Open Universe Assume that, the universe is expanding as observed by Hubble's telescope. Things farther away accelerate faster. The pushing force from the big bang and dark energy may be higher than the gravitational force from the mass of the universe. If the mean density of the universe is less than the critical density, the gravitational force of attraction cannot exceed the pushing forces, the universe will expand continuously forever on a divergent path. As a result, the universe will infinitely large. Every heavenly object will move away from others and remain alone. Such a scenario is called heat death or also called 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. 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. Reasonable Fact 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 4 Make a 3D model of the open universe. Fact File If mean density of the universe is less than critical density then the universe expand into saddle shape called open universe.

Oasis School Science and Technology - 10 329 Flat Universe As explained before, the universe will be closed if gravitational force can counter the expansion of the universe and open if gravitational force cannot counter the expansion of the universe. Various experiments, however, have suggested that the universe may be flat. The concept of the flat universe serves as a boundary between the open and closed universes. Assume the mean density of the universe equals the critical density then the masses in the universe that can produce gravitational force which is exactly equal to the expansion of the universe. Then the gravitational force will significantly counter the expansion. The rate of expansion will decrease slowly. 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. Thus, the universe is said to be a flat universe, in case the gravitational force 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 various kinds of universes depending on their structure. In this section, we shall display these universes using a graph. Open Flat Close omega point alpha point Radius of the Universe now time Fig: Types of universe Fact File The flat universe is flat in shape. It does not have any curvature. Fact File If mean density of the universe is equal to the critical density then the universe will be flat shape called flat universe.

330 Oasis School Science and Technology - 10 Reasonable Fact 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 5 What evidence suggest that the universe is flat? Discuss with friends. Use Wikipedia to confirm the conclusion of your discussion. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. There is a layer of air around the earth. The air does not escape away from the earth but stay as an atmosphere. Despite air is light, it does not escape away from the earth but stays around it. The layer of air forms the atmosphere. It happens because air has mass. The gravitation between the earth and the atmosphere binds them together. So, air cannot escape. 2. Mention 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. 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. 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. 3. As observed through the James Webb telescope, the stars further away from the earth are redder. What could be the reason? As observed from the James Webb telescope, the stars further away are redder. It means the rays of light that originated from those galaxies which has reached us are redshifted. The redshift suggested that those galaxies are moving further away from the earth every second. It also means the universe is expanding and galaxies are accelerating. 4. Compare between open universe and close universe. The comparison between open universe and close universe are listed below:

Oasis School Science and Technology - 10 331 SN Open universe SN Close universe 1 In this universe, matter will continue to expand forever in divergent path. 1 In this universe, matter will continue to converge. 2 The expanding force is greater than gravitation. 2 The gravitation is greater than expanding force. 3 The open universe is curved like the surface of the saddle. 3 The closed universe is spherical or elliptical. 5. Let’s suppose there is an open universe, how would it probably end? Let’s suppose there is an open universe it would probably end with a big chill. The open universe expands in a divergent path. Each matter is moving further away from the other and they are accelerating too. So, in distant future, each object will move so far away from the other that there won’t be next object around it. The universe will be in equilibrium. No energy flows in the universe. No work can be done in the universe. No new star would be formed. The universe will be cold and dark. Such a situation is called a big chill. 6. Suggest the shape and fate of the universe based on its critical density. The fate of the universe based on its density is listed below: 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. 7. Why 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. 8. 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. 9. 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.

332 Oasis School Science and Technology - 10 Exercises 1. Select the best answers from the given alternatives. a. Who introduced the big bang theory? i. Edwin Hubble ii. Georges Lemaitre iii. Albert Einstein iv. Redshift b. What is the reason that the solar system exists? i. the gravitation among the sun and other members. ii. the expansion forces from the big bang. iii. fault in space and time. iv. the galaxies around the milky way. c. What is Hubble’s law? i. The velocity of the galaxies are proportional to their distance from earth. ii. Gravitation is directly proportional to the product of masses iii. Expansion is directly proportional to gravitation. iv. Gravitation is inversely proportional to the square of the distance. d. If the universe is expanding, why is the distance between the sun and earth not increasing? i. Gravitation is stronger than expanding forces. ii. Expanding force is very weak. iii. The earth and the sun are one object. iv. The gravitation and expansion force almost balance each other. e. Why don’t planets collide while orbiting around the sun? i. They repel each other. ii. They pull each other. iii. They are pulled by sun. iv. They revolve in their own fixed orbit. f. What is the conclusion of Hubble’s observation? i. earth is flat ii. universe is flat iii. universe is expanding iv. universe is an illusion 2. Define the following terms with appropriate examples. a. Universe b. Gravitation c. Galaxy d. Black hole e. Big bang theory f. Close universe g. Open universe h. Flat universe i. Big crunch j. Big chill k. Critical density l. Big bang force 3. Answer the following question. a. Which force keeps heavenly objects bound together in a group? b. Which hypothesis on origin of the universe is most valid yet? c. How did universe come to be based on the big bang theory? d. What are the conditions required for the universe to be flat? e. What is the meaning of H in Hubble’s law, v =Hd? 4. Give reasons. a. Excessive gravitation can produce a close universe. b. Open universe is formed if gravitation is weaker.

Oasis School Science and Technology - 10 333 c. Balance between gravitation and expansion forces is key to a flat universe. d. A closed universe will end with a big crunch. e. Satellites revolve around the planet. f. Gravitation forms galaxies. g. The big bang theory is the most reliable. h. The surrounding galaxies are moving away from the milky way. i. Earth revolves around the sun and moon revolves around the earth, but they do not collide. 5. Differentiate between the followings: a. Gravitation and expanding force from the big bang b. Flat universe and close universe 6. Answer the following questions in short. a. What is the proof of the big bang? b. What end awaits the open universe? c. Enlist the effects of gravitation. d. What is the role of gravity in the formation of solar system? e. What will the universe be like if the gravitation balances expansion force just right? f. Is our universe close, open or flat, what does the observation suggest? 7. Answer the following questions on the basis of the given figure. i. Which model of the universe is above picture trying to represent? ii. What can cause the creation of such a universe? iii. How will such a universe come to an end? 8. Answer the following questions. a. Is the universe expanding? Put your opinion with a suitable explanation. b. What are the conditions for a universe to be closed, open or flat? c. How will a close universe and a flat universe meet their end? d. Describe the big bang theory. e. How do Hubble’s observations support the big bang theory? 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. g. What would be the fate of the universe based on its shape? What is the shape of the universe based on observation? Support your answer.

334 Oasis School Science and Technology - 10 UNIT 13 INFORMATION AND COMMUNICATION TECHNOLOGY Estimated teaching periods Theory 5 Practical 5 • 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 well-being • 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) The Sequence of Curriculum Issued by CDC 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. About the Scientist Claude Elwood Shannon Key terms and terminologies 1. ICT : ICT is a diverse set of technological tools and resources which are used to transmit, store, create or exchange information. 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.

Oasis School Science and Technology - 10 335 8. Digital 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. 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 The ICT (Information and Communication Technology) refers to a broad range of products and services related to calculating, data management, telecommunications, and the internet. The transmission and reception of various kinds of information and communications are covered by ICT. In many ways, ICT is essential. For example, it improves communication channels, reduces costs, does away with paper, offers better teaching and learning techniques, enhances data and information security, does away with loss of data, saves time, and so far. Therefore, ICT is a diverse set of technological tools and resources which are used to transmit, store, create or exchange information. Electronic signals are necessary for the efficient operation of digital devices and technology. Signal All the functions of ICT are based on electronic signals. A signal can be defined as an electromagnetic or electrical circuit that is used for carrying data or information from one source or device or network to another. A signal is an essential component of telecommunication, computing, networking, and electronic devices. Signals are also used to communicate and send instructions by processors, memory, storage, and a variety of other components. A signal can be either analog or digital. Each signal contains data in some form. It is created when a command or data is sent to a device. In this way, the complex function of ICT is carried out. There are two types of signals. They are analog signal and digital signal.

336 Oasis School Science and Technology - 10 Analog signal An analog signal is a continuous electrical signal whose value changes with time. These signals work with physical values and natural phenomena such as earthquakes, frequency, volcanoes, wind speed, sound, temperature, and so on. Digital signal Digital signals are represented by binary numbers 0 and 1. It is used in all digital electronics including computer, mobile and data transmission devices. Digital signal is a non-continuous electrical signal having discontinuous (discrete) values with time. 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 Reasonable Fact The graph of digital signal is discontinuous. 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. 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. They cannot be represented by binary numbers 0 and 1. 2. They are represented by binary numbers 0 and 1. 3. ADC (analogue digital converter) converts digital signals into analogue signal. 3. DAC (digital analogue converter) converts analogue signals into digital signal. 4. Graphically, analogue signals are represented by sign wave. 4. Graphically, digital signals are represented by square wave. Fig: analog signal Fact File Sine waves are used to show an analog signal, while square waves are used to show a digital signal. Fig: digital signal

Oasis School Science and Technology - 10 337 Concept of Bit and Byte Bit Bit is actually a single unit of information reflecting a zero (off/false) or a one (on / true). It is an abbreviation of binary digit. Thus, a bit is the smallest unit of computer memory which has the capacity to store a maximum of two different values 0 or 1. 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 a set of 8 bits. There are altogether 256 distinct combinations of these 8 bits. These combinations cover the alphabets, special characters and many more. Thus, byte is the basic unit of computer data storage in the set of 8 bits. 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 stands for binary digit. 1. Byte stands for binary elementary string. 2. Bit is the smallest and fundamental unit of computer data system. 2. Byte is the basic unit of computer data storage which is the set of 8 bits. 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’. Digital Signal Transmission Digital signal transmission 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. Thus, digital signal transmission is the process of sending information over physical communication media in the form of digital signal. Fact File Do you know that ‘0’ of digital signal represents ‘low voltage’ and ‘1’ represents ‘high voltage’? Fact File 1 Byte = 8 bits Digital electronic devices use digital signal for their operation. Fact File Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte are the multiples of byte.

338 Oasis School Science and Technology - 10 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 In baseband transmission, we send digital signals without converting them into analogue signals. Thus, 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. 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. Advantages of baseband transmission i. It is easier to use because of its simple structure. ii. It has low installation cost. 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. B. Broadband Transmission In broadband transmission, we send digital signals converting them into analogue signals. Thus, 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. Fig: Baseband transmission Fact File 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. Fact File Low pass channel or baseband channel is a communication channel that can transfer frequencies that are very close to zero. Fact File Modulation is a process of converting a digital signal to analog signal or vice-versa. Amplitude Bandpass channel Frequency f1 f2 Broadband Transmission

Oasis School Science and Technology - 10 339 Broadband transmission uses optical fiber cables, co-axial cables and radio waves for its transmission. Uses of broadband transmission It is mostly used for the telephone network as the broadband signaling. It can be transmitted for a long distance. Advantages of broadband transmission i. It offers greater bandwidth. ii. It supports the transmission of data, voice and video. iii. It can be used for long distance transmission. Disadvantages of broadband transmission i. Its maintenance is quite difficult. ii. Its cabling is complex. iii. Its installation cost is expensive. Components of digital communication system There are following components of digital communication system. i. Encoder: It converts data into minimum bit number. It helps easy transmission of signals. ii. Modulator: It modulates signals and converts into analogue signal. After converting into analogue signals, modulator gives direction to pass into medium or channel. iii. Channel: Channel or medium provides path for analogue signal from transmitter to the receiver. iv. Demodulator: It demodulates signals obtained from receiver. v. Decoder: It digitized the demodulated signals so that there will be less error in the output signals. i. Source: For digital communication the source is analogue signal. ii. Input transducer: It converts input signals into electric signal. For example, microphone converts sound into electricity. vi. Output transducer: It converts decoded signals into original physical quantity. For example, loud speaker converts electricity into sound. vii. 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. Fact File Bandpass channel is a communication channel whose bandwidth does not start from zero.

340 Oasis School Science and Technology - 10 Source Transmitter Receiver Sink Message Encoder Message decoder Channel decoder Channel Encoder Modulator Analog Channel Demodulator 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. It needs less bandwidth. 1. Digital communication transfers data converting analogue signals into digital signal and finally into analogue signal. It needs more bandwidth. 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. Advantages of digital transmission 1. Compared to analogue circuits, digital circuits are easy and fast to design. 2. Digital transmission is less affected by outside noise or factors. 3. The digital transmission circuit is reliable. 4. There is less overlapping and crossing when digital signals are sent. 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. Most of the time, the characteristics of digital signals don't change. Effects of digital technology in the development of information and communication When digital technology is getting better, both information and communication are getting better as well. Digital technology is used more in communications, the internet, digital media, digital TV, and other areas. 1. Digital TV Digital technology is used to make the high definition TVs. It is used to send news, information, and other things all over the country. Fig: digital and analogue TV

Oasis School Science and Technology - 10 341 2. Digital telecommunication Digital telecommunication makes communication fast. As a result, we can connect many phones together. 3. Digital media Digital media is the way in which electronic devices are used. With the help of these electronic devices, we can watch the news, send online information, make digital media, etc. Effects of Digital Technology in Human Life It is said that the 21st century is the Age of Science and Technology. In the last few decades, many new technologies have been made and improved. Digital technology has grown advance 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. A. Positive aspects of digital technology The digital technology and the computing system are mostly used in our life, from communication to finances to social interactions. 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 important things that the Internet has changed and made better. 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 any time, any where whoever wants. Fig. digital telecommunication Fig. digital media

342 Oasis School Science and Technology - 10 2. Social Network With the development of digital technology, social media like Facebook, Instagram, Whatsapp, Viber, etc. have made it easier to connect with others and make new friends. 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 With the development of digital technology, the banking sector has become easier. People can do almost all of their banking online. 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 payment in any fields, such as online booking of means of transportation, entertainment and so on. 4. Business One of the most important things the Internet offers is a way to do business. Using different apps, online shoppers can buy almost anything at any time from the comfort of their own homes. 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.

Oasis School Science and Technology - 10 343 5. Health Access to health information on the Internet improves care, gives you access to medical or health information 24 hours a day, and makes it easier to deal with 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 Laptops, mobiles, tablets, etc. are also used in many other areas. 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 The digital technology has become a important aspect of our daily lives. There are some good things about digital technology, but there are also some bad things. 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. Physical health effects Continuous and regular uses of digital technology may increase the risk of eyestrain, bad posture, sleep problems, obesity, less physical activity, etc. 2. Learning barriers We are slowly forgetting things. It is because we know every thing can look it up online in a seconds. It is also found that students are more likely to remember where to get the information rather than remembering the information itself. 3. Psychological effects If you use technology too much or depend on it too much, it could hurt your mind. It includes isolation form family and friends, depression and anxiety which make a person mentally ill. 4. Cyber bullying Cyber bullying is an activity that hurts, humiliates, or threatens someone else by sending or posting messages using the Internet, cell phones, video game systems, or other technology. 5. Terrorism and crime Many people do illegal activities on the Internet on the dark web. The identity of a person can be made hidden and it becomes difficult to track the person or Fact File 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.

344 Oasis School Science and Technology - 10 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 various activities like stealing, editing, and posting other people's photos, videos, and digital data have made it harder to protect privacy and keep a record 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 are active members of 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 1. While using the digital media, a good digital citizen or netizen knows what kinds of websites, apps, and online interactions to avoid and what kinds of websites are good sources of information. 2. When leaving comments on Facebook, Instagram, or Twitter, a good netizen should be very careful so that they do not even put us in risk or harm others. 3. A good netizen should not share others’ private message, pictures, videos, etc. to the whole world without the consent of the person. 4. A good netizen should not download, copy or share other’s data without author’s permission or unless it is free. 5. A good netizen should never criticize someone else without knowing the truth about the issue. Reasonable Fact Digital footprint is 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. Fact File Digital footprint is a data that is left behind by a netizen while using internet.

Oasis School Science and Technology - 10 345 Digital Wellbeing (Netiquette) Nowadays, we see more and more manners problems, like spreading fake news, cyberbullying, trolling, and many others. 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. Avoid sharing fake news: Before you share any kind of information, you should make sure you can trust it. Fake news may make others to take bad decision or even may create panic. ii. 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. iii. 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. iv. Respect others’ privacy: A netizen should not share others’ private message, pictures, videos, etc. to the whole world without the consent of the person. 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. Use your influence wisely: A netizen does not have right to judge others even if a person has millions of followers. ix. 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. A person who uses the Internet should always follow the rules of netiquette. Always try to be a better Internet user. Online Reputation While using Internet, we see a variety of things online. Once they say something, we like it, share it, and talk about it. In the same way, we can see what others have said about us and what they have shared about us. It affects how other people see each other. 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. Fact File Online reputation is judged from the likes, shares and comments about a person, company or organization.

346 Oasis School Science and Technology - 10 Factors affecting Online Reputation i. Technological problems: If a company's server has technical problems, whether they are financial or institutional, it can hurt their reputation. ii. Spread of misinformation: Spread of misinformation about the individual or company through Internet can quickly damage a reputation. iii. Bad reviews: Bad reviews always act as repellent for the customers towards the brand. iv. Security breaches: An organization loses its reputation if it is unable to protect or secure its digital data from being hacked and manipulated. v. Social media: The negative comments are rapidly spread through social media. They affect reputation of an individual or of an organization. Reasonable Fact Online reputation affects 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) It is important for a person, institution, company, business, etc. to have online reputation management. Thus, 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. Attend: Respect and give importance to the opinions of users and followers. ii. Communicate: Every time give correct business information and internet content. iii. Monitor: Always check for the negative comments or attacks on the online reputation of the brand. iv. Apology: Any occurrence of errors in company’s content or information must be evaluated, corrected along with the apology for the incorrect information. v. Respond: Always give correct and polite answers to questions and doubts from users and followers, especially when they are negative. Reasonable Fact Online reputation management is important. The online reputation management (ORM) is important to establish an accurate, sustainable and controllable background about the company, brand, organization or a person. Fact File One can lose online reputation, if digital etiquette is not followed. Fact File To prevent an organization, brand and person from being victim of reputation loss, Online Reputation Management(ORM) is necessary.

Oasis School Science and Technology - 10 347 Activity 1 Make a visit to 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 Everyone uses their phone or computer to record audio and video. The aim of the recording depends on the person and the work they do. 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. Audio Recording A. From laptop and computer Some laptops and some desktop computers have microphones built in, but the rest don't. 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.

348 Oasis School Science and Technology - 10 B. Voice recording in an iPhone All iPhones come with a built-in voice recorder that can't 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 Many Android smartphones come with a bunch of software already on them. It comes with a program that lets you record your voice, such as "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 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. There are many webbased 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.

Oasis School Science and Technology - 10 349 Step 1 : Go to https://online-voice-recorder.com/beta/ from any web browser. Step 2 : Click on ‘Allow M i c r o p h o n e 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 As we listen to music or other audio, some parts of the track can be too interesting. 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. Step 1 : Open the Music Editor application. Step 2 : Choose ‘Trim Audio’. Browse music library to locate the file 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 should be cut (or drag and drop your 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. We can perform some other editing like changing pitch, volume or speed of the audio. Fact File Online audio/video cutter/trimmer is available in internet and can be used free of cost.

350 Oasis School Science and Technology - 10 Merging or joining audio files into one (Online) With an online app like Online Audio Joiner, you can combine two or more audio files into one. 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) Few off-line programs can combine 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 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.