# Physics Paper 3 Questions and Answers with Confidentials - MECS Cluster Joint Mock Exams 2021/2022

PHYSICS
PAPER 3

PRACTICAL

INSTRUCTIONS TO CANDIDATES

•  Answer ALL questions in the spaces provided in the question paper.
• You are supposed to spend the first 15 minutes of the allowed for this paper reading the whole paper carefully before commencing the work.
• Marks are given for a clear record of the observations actually made, their suitability, accuracy and the use made of them.
• Candidates are advised to record their observation as soon as they are made.
• Non programmable silent electronic calculators may be used.
• This paper consists of 8 printed pages.
•  Candidates should check the questions to ascertain that all the pages are printed as indicated and that no question are missing.
• Candidates should answer the questions in English.

QUESTION 1 (20 marks)

1. You are provided with the following;
• A galvanometer
• A dry cell and a cell holder
• A switch
• A wire labelled Y mounted on a piece of wood.
• Eight connecting wires each with a crocodile clip at one end.
• A resistance wire labelled AB mounted on a millimeter scale.
• Six 10 Ohm carbon resistors
• A jockey or crocodile clip
• Micrometer screw gauge (to be shared)

Proceed as follows:
1. Set up the circuit as shown in figure below, with X being one of the 10 ohms carbon resistors. 2. Close the switch. Tap the jockey at various points on the wire AB and locate point P at which the galvanometer shows zero deflection, measure and record in table below the length, where = PB.
3. Repeat the procedure in (b) using X as two 10Ω resistors, three resistors, four resistors, five resistors and six resistors. X is the effective resistance for the parallel combination i.e. x = 10/n where n is the number of resistors in parallel.
TABLE
 Number of 10ΩCarbon resistor One Two Three Four Five Six X (Ω) L (cm) 1/x (Ω-1) 1/L(cm-1)
5. Plot a graph of 1/L (y-axis) against  1/x. (5mks)
6. Determine the slope m of the graph. (2mks)
7. Given that 1/L = R/KX + 1/K where K = 100cm. Use the graph to determine R. (2mks)
8. Measure the diameter d and the length of wire Y. (2mks)
=…..……..…………………………..….m
d = ………….…………………………….. m
9. Determine its cross-sectional area A of the wire Y. (1mk)
A =………………………………………… m 2
10. Determine the resistivity of the wire Y given that its Resistance, R= 1/A(2mks)

QUESTION 2 (20 marks)

PART A

You are provided with the following;

• Meter rule
• Retort stand, clamp and boss
• A spring and with a pointer
• Three masses (a 100 g and two 50g masses)
• Stop watch

Proceed as follows

1. Set the apparatus as shown below. xo………………………………………………………….…………………………. m. (1mk)
3.
1. Load a mass of 150 g and determine the extension of the spring, e1 .
e1……………………………………………………………………………. m. (1mk)
2. Displace the 150 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t1 t1 ………………………………………………….. (1mk)
3. Find periodic time T 1
T1 …………………………………………………. (1mk)
4. Use the equation to find the value of P-1 . (2mks)
4.
1. Load a mass of 200 g and determine the extension of the spring, e2 .
e2……………………………………………………………………………. m. (1mk)
2. Displace the 200 g mass slightly downwards and release it to oscillate vertically.
Time 20 oscillations and obtain time t2 .
t2 ………………………………………………….. (1mk)
3. Find periodic time T1
T1 …………………………………………………. (1mk)
4. Use the equation to find the value of P2 . (2mks)
5. Find the average of P (2mks)
Pav = P² + P¹
2

PART B

Apparatus
• Lens and a lens holder
• A candleScreen
• A metre rule.

Procedure
6. Focus a distant object and estimate the focal length, f of the lens
f …………………………………………. mm. (1mk)
7. Set up the apparatus as shown below. 8. Set the distance s= 60 cm.
1. Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
P =………………………………………. cm. (1mk)
2. Maintaining distance s, adjust the lens to position P’ where a diminished sharp image is formed on the screen. Record position, P’.
P’ = ……………………………………… cm. (1mk)
3. Find distance d, between the original position and final position of lens
d = ………………………………………... cm (1mk)
9. Using the formula s2 - d2 = 4 Find the value of q. (2mks)
10. What physical quantity do q represent (1mk)

CONFIDENTIAL

QUESTION 1

Each candidate will require

• Centre zero galvanometer
• One new size D dry cell &amp; cell holder
• A switch
• Eight connecting wires each with crocodile clip at one end.
• A piece of nichrome wire swg 28 (diameter 0.32 mm) of length 30cm.
• Teacher to mount the piece of wire on piece of wood and label it Y see • A resistance (nichrome wire gauge 30) wire labeled AB 100cm long mounted on a millimeter scale
• Six 10 Ohms carbon resistors.
• A jockey (a crocodile clip may be used)
• A micrometer screw gauge

QUESTION 2

Each candidate will require:

• A spiral spring of spring constant of approximately 10.0N/m.
• A complete stand
• A metre rule.
• Lens (focal length = 10cm) and a lens holder.
• A candle
• Screen
• Three masses (one 100g and two 50g masses)
• A stop watch

MARKING SCHEME

QUESTION 1 (20 marks)

1. You are provided with the following;
• A galvanometer
• A dry cell and a cell holder
• A switch
• A wire labelled Y mounted on a piece of wood.
• Eight connecting wires each with a crocodile clip at one end.
• A resistance wire labelled AB mounted on a millimeter scale.
• Six 10 Ohm carbon resistors
• A jockey or crocodile clip
• Micrometer screw gauge (to be shared)

Proceed as follows:
1. Set up the circuit as shown in figure below, with X being one of the 10 ohms carbon resistors.
2. Close the switch. Tap the jockey at various points on the wire AB and locate point P at which the galvanometer shows zero deflection, measure and record in table below the length, where = PB.
3. Repeat the procedure in (b) using X as two 10Ω resistors, three resistors, four resistors, five resistors and six resistors. X is the effective resistance for the parallel combination i.e. x = 10/where n is the number of resistors in parallel.
 Number of 10ΩCarbon resistor One Two Three Four Five Six X (Ω) 10 5 3.333 2.5 2 1.667 (L cm) 66.5 53.3 48.2 43.5 40.2 37.4 1/x (Ω-1) 0.1 0.2 0.3 0.4 0.5 0.6 1/L(cm-1) 1.515 1.876 2.075 2.299 2.488 2.674

Plot a graph of 1/L (y-axis) against 1/x. (5mks) 5. Determine the slope m of the graph. (2mks)
• m = (2.2 - 2.5) 10‾² cm-1
(0.35 - 0.10) -1
(Correct substitution = 1mk)
(Correct evaluation with units = 1mk)
Wrong unit = 0mk, no unit = half mark

6. Given that where 1/L = r/KX + 1/K where K = 100cm. Use the graph to determine R. (2mks)
• Slope = R/K
(Correct substitution = 1mk)
=28
(Correct evaluation = 1mk)

7. Measure the diameter d and the length of wire Y. (2mks)
• I = 30.0/100 = 0.300 m ±0.01 (Value within the range and 3dp a must = 1mk)
d = 0.32/100= 0.0032m ± 0.00002(Value within the range and 5dp a must = 1mk)

8. Determine its cross-sectional area A of the wire Y. (1mk)
• (Correct substitution = mk)
A m2 (Correct evaluation = mk)

9. Determine the resistivity of the wire Y given that its Resistance, (2mks)
• 7.508 x 10-7m
(Correct substitution = 1mk)
(Correct evaluation = mk, rule for units applies)

QUESTION 2 (20 marks)

PART A

• You are provided with the following;
• Meter rule
• Retort stand, clamp and boss
• A spring and with a pointer
• Three masses (a 100 g and two 50g masses)
• Stop watch

Proceed as follows
1. Set the apparatus as shown below.
• xo = student value (3d.p a must) m (1mk)
3.
1. Load a mass of 150 g and determine the extension of the spring, e 1 .
• e1 = difference in student values = 0.148 ± 0.0 m (1mk)
(Correct subtraction = mk, correct evaluation =mk)

2. Displace the 150 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t 1 .
• t 1 = 16.37 ±  0.5 (1mk)
(Value within the range and 2dp a must = 1mk, no unit deny a half mark)

3. Find periodic time T 1
• T 1 = 16.37/20 = 0.8184s
(Correct division = mk, correct evaluation with unit=mk)
(1mk)

4. Use the equation to find the value of P 1 . (2mks)
• P = 0.148/0.01616 = 9.158 m/s2
(Correct substitution = 1mk)
(Correct evaluation to 4sf = 1mk)
4.
1. Load a mass of 200 g and determine the extension of the spring, e 2 .
• e2 = x2 - x0 = 0.196 ±  0.01 m. (Correct subtraction =
mk, correct evaluation=mk). (1mk)

2. Displace the 200 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t 2 .
• t 2 = 18.62 ±  0.5s (1mk)
(Value within the range and 2dp a must = 1mk, no unit deny a half mark)

3. Find periodic time T 1
• T2 = 18.62/20 = 0.9310s
(1mk) (Value within the range and
2dp a must = 1mk, no unit deny a half mark)

4. Use the equation to find the value of P2 . (2mks)
• (Correct substitution = 1mk)
(Correct evaluation to 4sf = 1mk)

5. Find the average of P
• (Averaging principle = 1mk). (2mks)
(Correct evaluation to 4sf = 1mk)

PART B
Apparatus
• Lens and a lens holder.
• A candle
• Screen
• A metre rule.

Procedure

6. Focus a distant object and estimate the focal length, f of the lens
• f mm ± 10 mm (1mk)

7. Set up the apparatus as shown below.
8. Set the distance s= 60 cm.
1. Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
• P = Student’s value (1d.p a must) cm. (1mk)

2. Maintaining distance s, adjust the lens to position P’ where a diminished sharp image is formed on the screen. Record position, P’.
• P’ = Student’s value (1d.p a must) cm. (1mk)

3. Find distance d, between the original position and final position of lens
• d = cm (1mk)
(Correct subtraction = mk, correct evaluation =mk)
9. Using the formula . Find the value of q. (2mks)
• (Correct substitution = 1mk)
• (Correct evaluation to 4sf = 1mk)

10. What physical quantity do q represent (1mk)
• Focal length of the lens used.

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