PRE-LAB MODULES
(LECTURER’S COPY)
PHYSICS SP025
KOLEJ MATRIKULASI NEGERI SEMBILAN
SP025 Pre-Lab Module ANSWERS
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 1: CAPACITOR
Objectives:
At the end of this lesson, students will be able to explain the experiment:
(i) To determine the time constant, τ of an RC circuit.
(ii) To determine the capacitance, C of a capacitor using an RC circuit
Student Learning Time:
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read over the lab manual and then answer the following question.
Introduction
1. A capacitor is a device that can store electric charges or electric potential energy.
2. Capacitance of a capacitor is the ratio of the charge on either plate to the potential difference
between them.
3. ‘For discharging process, the magnitude of discharge current is given by = − − ‘
The negative sign shows that current flows during discharging process in opposite direction as the
current flows during the charging process.
4. What is the relationship between time constant, and capacitance, C.
= RC where is directly proportional to C.
5. Time constant is defined as the time taken of a discharge current to decreases to 37% of its
maximum current.
Experiment
6. Sketch and label two circuit diagrams of the experiment?
7. Before starting or repeating the experiment, why we need to short circuit the capacitor?
To make sure the capacitor in fully discharged.
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SP025 Pre-Lab Module ANSWERS
8. From this experiment, identify
a. the manipulated variable: current
b. the responding variable: time
9. Why large resistance is used in the experiment?
To protect capacitor from damage
Data Analysis
10. Two capacitors, C1 and C2 can be connected either in series or parallel.
Write the formula of effective capacitance for the following connection.
Series : 1 = 1+1
1 2
Parallel : Ceff = C1 + C2
11. Which circuit connection will discharge faster? Explain your answer.
Series circuit. It is because series circuit has small capacitance compare to the parallel circuit.
12. Sketch and label a graph that need to be plotted in this experiment.
ln o
0 t (s)
13. How to determine time constant, from the graph.
From equation ln ( o) = , gradient of the graph, = 1. So = 1 .
14. Explain steps to calculate the value of capacitance of capacitor in this experiment.
1. Time contant, is determined from the gradient of the graph where = 1
2. Use = to calculate C
15. State THREE precautions of these experiment.
1) Make sure the capacitor is fully discharged before starting or repeating the experiment by
short circuiting the capacitor using a wire.
2) Make sure the connection wires to the micro ammeter and capacitor are correct to avoid the
capacitor from damage.
3) Avoid using too many wires / long wire to reduce energy loss.
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 2: OHM’S LAW
Objectives:
At the end of this lesson, students will be able to explain the experiment:
i. sketch V – I graph.
ii. verify Ohm’s Law.
ii. determine effective resistance, Reff of the resistors in series and parallel by graphing method.
Student Learning Time (SLT):
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read over the lab manual and then answer the following questions.
Introduction
1. Define Ohm’s Law.
Ohm’s Law states at a constant temperature, the potential difference across the conductor is directly
proportional to the current across the conductor.
2. Sketch a graph of Voltage,V against Current,I for an Ohmic device and explain how you can obtain
the resistance of the device from this graph.
R = gradient of the graph
3. The effective resistance (Reff) increase. (increase / decrease / constant) as resistors are added in
series and is obtained by adding the individual resistances :
Reff = R1 + R2 + R3 + …+ Rn
4. The effective resistance (Reff) decrease (increase / decrease / constant) as resistors are added in
parallel and is calculated as :
1 = 1 + 1 + 1 +⋯+ 1
1 2 3
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SP025 Pre-Lab Module ANSWERS
5. Suppose you have a circuit consisting of three identical resistors, R = 27 Ω and a power supply.
a) If the resistors are connected in series, sketch the circuit diagram and find Reff for the THREE
resistors.
Diagram Calculation
eff = 1 + 2 + 3
eff = (27 + 27 + 27) Ω
eff = 81 Ω
b) Repeat part (a) for the case if the three resistors are in parallel.
Diagram Calculation
1 =1+1+1
eff 1 2 3
1 = (1 + 1 + 1)Ω̶1
ff 27 27 27
eff = 9 Ω
Experiment
6. (a) As voltage applied to the resistors increase, current through the resistors will increase
(b) Identify the Voltage
Independent variable = Current
Dependent variable = Resistance / Number of resistors
Constant variable =
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SP025 Pre-Lab Module ANSWERS
7.
COLOR 1st 2nd Multiplier
Band Band Color
Band
Black 00 1
Brown 1 1 10
Red 2 2 102
Orange 3 3 103
Yellow 4 4 104
Green 55 105
Blue 66 106
Violet 77 107
Grey 88 108
White 99 109
Using the color chart above, decode the value of the following resistors and indicate the tolerance:
Example : Brown, Black, Red, Gold. (10 × 102 ± 5%) Ω
a) Yellow, Violet, Yellow, Gold. (47 × 104 ± 5%) Ω
b) Brown, Black, Green, Silver. (10 × 105 ± 10%) Ω
8.
FIGURE 2.1
Based on FIGURE 2.1, what is the function of Rheostat?
The function of the Rheostat is to control the specific quantity of current to flow through the
circuits.
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SP025 Pre-Lab Module ANSWERS
9. Based on FIGURE 2.1, why the milliammeter is connected in series but the voltmeter is
connected in parallel?
i) Milliammeter is connected in series because milliammeter measures the rate of charge
flow or electric current flow at one point.
ii) Voltmeter is connected in parallel because voltmeter measures potential differences
between two points.
10. In the experiment, milliammeter is used to measure current in series circuit but ammeter is used
to measure current in parallel circuit. Why?
Since in series circuits give larger effective resistance and produce smaller current thus
miliammeter is suitable. But for in parallel circuits, effective resistance is smaller and produces
larger current thus ammeter is suitable.
Data Analysis
11.The equation uses to plot the graph is V = IR.
Sort the quantities from the equation according to its components below:
y – axis =V
x – axis =I
m – gradient =R
12.What is the unit for the gradient
Series = V mA-1 or kΩ
Parallel = V A-1 or Ω
13. If your experiment follows Ohm’s law, what type of the graph you are supposed to get.
Linear graph. V directly proportional to I.
14. Which of the graph is expected to have a bigger gradient, the series or the parallel
circuit? Explain your answer.
As the gradient is the effective resistance for the resistors arrangement, resistor arrange in series
has a larger effective resistance, thus gradient V against I for series resistors is larger.
15. List down THREE precautions of the experiments.
Make sure all the wires connected correctly the right terminal
Make sure use voltage 4 - 6 V only.
Make sure all the wires connected tightly in the circuit.
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 3: POTENTIOMETER
Objective:
At the end of this lesson, students will be able to explain the experiment to explain the experiment to
determine internal resistance, r of a dry cell by using potentiometer.
Student Learning Time:
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read over the lab manual and then answer the following question.
Introduction
1. What is the difference between accumulator and dry cell?
Accumulator Dry cell
✓ Has no internal resistance ✓ Has internal resistance
✓ Rechargeable ✓ Not rechargeable
2. How to balance the circuit(s) by using the jockey?
The jockey is tapped until no deflection (galvanometer = 0).
3. Write the equation of electromotiveforce,Ɛ in terms of potential difference, V and internal
resistance, r. Define all symbols.
Ɛ = V + Ir
where Ɛ = emf , V = potential difference/ terminal voltage , I = current in the circuit, r = internal
resistance.
4. Copy FIGURE 3.1. Sketch the direction of current flow when S1 is closed and S2 is opened.
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SP025 Pre-Lab Module ANSWERS
5. Copy FIGURE 3.1. Sketch the direction of current flow when S1and S2 is closed.
Experiment
6. a. Manipulative variable : Resistance, R
b. Responding variable : Length, l
c. Constant variable : Internal resistance, r
7. Predict what happen if you change polarity of the dry cell?
The galvanometer will deflect in different direction.
8. What is the function of variable resistor in this experiment?
Variable resistor is used to control voltage and/or currents. Its able to have its
electrical resistance adjusted.
9. Why the jockey should not be drag on the wire, instead the jockey should be pointed carefully?
Because the dragging or rubbing of wire with jockey can change the uniformity of the cross
sectional area of the wire and thereby affecting the fall of the potential along the wire.
10. What is the relationship between resistance and the length of wire?
r is directly proportional to l.
Data Analysis
11. The internal resistance can be determine by using related equation. Write the equation in
terms of l,r and R that satisfy y = mx + c.
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SP025 Pre-Lab Module ANSWERS
0 = 1 + 1
( )
12. Sketch an appropriate graph of 0 against 1.
0
gradient, m
1
13. What does the gradient of the graph represent?
Gradient, m is equal to internal resistance, r.
14. State the physical quantities and unit that can be obtain from the gradient, m.
Physical quantities are resistance and unit is Ω.
15. List THREE precautions of the experiment:
i. Make sure all wires connected properly.
ii. Do not drag the jockey along the wire.
iii. Use a new dry cell for each experiment.
iv. Before starting the experiment, ensure that when jockey is at point A and B, the galvanometer
needle will deflect in opposite direction.
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 4 (a) : MAGNETIC FIELD
Objective:
At the end of this lesson, students will be able to explain the experiment to determine the value of the
horizontal component of the earth magnetic field, BE.
Student Learning Time:
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read over the lab manual and then answer the following question.
Introduction
1. What is the quantity of magnetic field (intensity), B ?
Vector quantity.
2. What is the symbol and SI unit for magnetic field?
Symbol Magnetic Field = B
SI Unit = Tesla (T)
3. The addition for two vector quantities of magnetic fields obeys the
Parallelogram law.
4. State the equation for magnetic field strength at the centre of the coil.
Bc = NI
D
5. (a) From the diagram below, state the equation for tan in terms of BE and BC.
tan = BC
θ BE
(b) Since Bc = NI , derive tan in terms of BE and I.
D
tan = BC tan = O NI
BE DBE
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SP025 Pre-Lab Module ANSWERS
Experiment
6. State the:
a. Manipulative variable : Current, I
b. Responding variable : Angle of deflection, θ
c. Constant variable : Number of turns of the solenoid, N
Diameter of a coil, D
Earth magnetic field strength, BE
7. What is the arrangement for the connection of the EM-0.1 kit, rheostat, ammeter, power supply
and switch in the lab?
All connection must be set up in series circuit.
8. What is the function of rheostat in this experiment?
To increase/decrease/vary the resistance therefore it will decrease/ increase/vary the electric
current (I).
9. What are the measuring apparatus used during the experiment?
Ammeter and compass.
10. Why does the compass has to be put away from any iron structure?
To avoid any influence on the alignment of the compass’s needle
11. Why do we have to change the polarity of the power supply and record the angle 2?
To find the average value of angle so that the result will be more accurate.
Data Analysis
12. Base on the linear graph equation y = mx + c, write the suitable quantity referring to equation in 5
(b).
(a) y-axis : tan θ
(b) x-axis :I
(c) gradient, m : m = N
DBE
(d) y -interception : none/ zero.
13. Base on the linear graph equation y = mx + c, sketch a suitable graph referring to equation in 5
(b).
m
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SP025 Pre-Lab Module ANSWERS
14. According to the straight line graph of tan θ against I, what is the relationship between tan θ and
I?
tan is directly proportional to I.
15. How do we determine the value of BE from this graph?
From the gradient of graph, m = N Therefore, BE = N
DBE Dm
16. List down THREE precautions for this experiment.
1. Carry out the experiment in an isolated environment because surrounding magnetic field (e.g
mobile, electrical wiring) may affect the readings of the experiment.
2. Keep away any electronic equipment.
3. Make sure the solenoid is perpendicular to the North of the compass.
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 5: GEOMETRICAL OPTICS
Objective:
At the end of this lesson, students will be able to explain the experiment to determine the focal length
of a convex lens.
Student Learning Time:
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read the laboratory manual and then answer the following questions.
Introduction
1. Write the thin lens equation and define each symbols.
1 11
= +
Where f = focal length
u = object distance
v = image distance
2. Convert the equation above into = − (1) + 1
Multiply equation by
(1 = 1 + 1) ×
= +
1
( ) = + 1
1
+ 1 = ( )
1
= ( ) − 1
However for real image, it is inverted. Therefore, magnification has to be -M .
Multiply the equation by (-)
1
− = − ( ) + 1
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SP025 Pre-Lab Module ANSWERS
3. Table 5.1
4. TABLE 5.1
Quantities Positive Negative
Object distance, u In front of lens / real object At the back of lens / virtual object
Image distance, v At the back of lens / real, In front of lens / virtual, upright
Focal length, f inverted Diverging / concave lens
Converging / convex lens
4. Draw a ray diagram to show the formation of image of a parallel beam of light incident on
a convex lens and state the position of the image formed (Procedure 1).
F1 O F2
Image is formed at the Focal point, F2 of the convex lens.
5. An object is placed at a distance (f < u < 2f) from the convex lens (Procedure 4).
a. Sketch the ray diagram to show the image formation.
b. State three characteristics of the image formed.
i. Real
ii. Inverted
iii. Magnified in size
Experiment
6. State the:
a. Manipulative variable: Object distance, u
b. Responding variable : Image height, hi and image distance, v
c. Constant variable : Focal length of the lens, f and height of object ho
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SP025 Pre-Lab Module ANSWERS
7. What is the relationship between the magnification, M and image distance, v?
Magnification, M is directly proportional to image distance, v.
8. Why does the focal length of the convex lens hav to be estimated?
To set the range of manipulative variable, object distance (f < u < 2f) as in Procedure 4.
9. How do we set up the convex lens to get the estimation of its focal length?
i. Choose a far away object outside the laboratory
ii. Adjust the screen back and forth until a sharp and inverted image is formed on the screen.
iii. Measure the distance from the screen to the lens. The value of v is equal to the festimate .
10. Label diagram below.
FIGURE 5.1
Data analysis
11. The focal length of a convex lens, f is related to its v and u also the magnification by the following
equation:
1 =1+1 …………………(1)
f uv
M =−v ………………………(2)
u
Rearrange equations (1) and (2) so that we can plot a straight line graph relating the variable M
and v.
- Multiple equation (1) with v
= + 1 …………(3)
- Substitute equation (2) into (3)
= − + 1 ………..(4)
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SP025 Pre-Lab Module ANSWERS
12. Based on the linear graph equation y = mx + c, write the suitable quantity being represented by
y-axis : Magnification, M
x-axis : Image distance, v
gradient, m: ̶ 1/f
y-intercept : 1
13. How to determine the focal length from the graph when M = ̶ 1 as in Procedure 10?
From the graph, extrapolate the image distance, v when = −1, and use the equation (4) to
get the focal length.
= − + 1
−1 = − + 1
−2 = −
=
2
14. Sketch the expected graph and state the physical quantities that can be obtain from the
gradient, m
M
y =mx + c is the
equation for this
straight line graph
v
15. State THREE precautions of the experiment
i. Make sure the lens is cleaned by methylated spirit to make sure there is no layer of oil or dirt
on the surface of the lens to get clearer image.
ii. Set up the light source, object, lens and screen in straight line because light travel in straight
line.
iii. Make sure that there are no other sources of light in the room so that it is easier to get a sharp
clear image.
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SP025 Pre-Lab Module ANSWERS
EXPERIMENT 6: DIFFRACTION GRATING
Objectives:
At the end of this lesson, students will be able to explain the experiment:
i. To determine the wavelength, of laser beam using a diffraction grating.
ii. To the number of diffraction grating lines per unit length,N.
Student Learning Time:
Face-to-face Non face-to-face
1 hour 1 hour
Instruction: Read over the lab manual and then answer the following question.
Introduction
1. What is the ray used in this experiment?
Laser beam.
2. What happen when a laser beam is incident on a diffraction grating?
When a laser beam is incident on a diffraction grating, a diffraction pattern in the form of a series
of bright dots can be seen on the screen.
3. Make a sketch of the diffraction pattern that you expect to see on an observation screen behind the
diffraction grating.
1st Bright Fringes
Central Bright Fringe
4. Based on equation sin = n , state the meaning of d in the equation.
d
d is the distance between two consecutive lines of the diffraction grating (grating spacing).
5. Based on equation sin = n , what is the relationship between angle, θ of nth order and wavelength
d
of laser beam?
Directly proportional
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SP025 Pre-Lab Module ANSWERS
Experiment
6. State the: : Number of order, n
i. Manipulative variable : Distance between the spot of order to the centre spot, l
ii. Responding variable : Distance between diffraction grating and screen, D
iii. Constant variable
7. Why we need to adjust the distance, D from the diffraction grating to the screen?
The distance, D from the diffraction grating to screen must be adjusted so that the spacing between
the spots on the screen is as far as possible from one another.
8. Suggest the best way to measure the length of each respective order of diffraction pattern on the
screen in procedure (3).
The length should be measured from the centre of Central bright fringe/spot to the centre of
respective (nth) fringe/spot.
9. How to determine the values of sin for order, n?
By using equation : sin = ln
(ln )2 + D2
Data Analysis
10. Write the related equation in order to determine the wavelength of laser beam, λ and number of
lines per mm of grating B.
sin = Nn
11. Based on linear graph equation y = mx + c, write the suitable quantity referring to equation in
question 11.
y – axis : sin
x – axis :n
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SP025 Pre-Lab Module ANSWERS
12. Sketch the suitable graph to show relationship between sin θ and order, n. Label the graph with
suitable symbol and write the title of the graph.
sin sin against n
n
13. (a) How do we determine the wavelength of laser beam, from the graph of sin θ against n?
gradient, m = N
= gradient, m where; N =100lines per mm
N
(b) Refer to the learning outcome (ii), how do we determine the number of lines per mm, N of
grating B from the second graph of sin θ against n?
gradient, m = N
N = gradient, m where; ( from step 6)
14. List THREE precautions of the experiment.
i. Ensure that the laboratory room is totally dark to precisely observe diffraction pattern on screen.
ii. Handle the diffraction grating with care as it is a delicate component. Do not scratch the surface
of diffraction grating or touch with fingers.
iii. Care should be taken that the reflected laser light is unlikely to enter any eye
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