# Physics Paper 3 Questions and Answers with Confidential - Lainaku II Joint Mock Examination 2023

INSTRUCTIONS TO CANDIDATES:-

• Answer all the questions
• You are supposed to spend the first 15 minutes of 2 ½ hours reading the whole paper carefully before commencing your work.
• Marks are given for a clear record of the observations actually made, their suitability, accuracy and the use of them
• Record your observations as soon as you make them.
• Mathematical tables, slide rules and silent non-programmable electronic calculators may be used.
• Take g = 10ms-2

Question 1

You are provided with the following

• A voltmeter 0−2.5 or 0−5 V
• A center zero galvanometer
• An ammeter
• Two new size D dry cells
• Two cell holders
• A switch
• Eight connecting wires each with a crocodile clip on one end
• A coiled resistance wire labeled X
• A resistance wire labeled AB mounted on a millimeter scale
• Six 10 carbon resistors
• A jockey/crocodile

Proceed as follows

1. Set up the circuit with the cells in parallel as shown in the figure below

2. With the switch open, record the reading E of the voltmeter
E = ______________ (1mark)
3. Close the switch and record the current I flowing through the circuit and the potential difference V across the cells
I = _______________ (1mark)
V = _______________(1mark)
4. Given that E = V + Ir and V = IR, determine the internal resistance r of the combined cells and the resistance (R) of the wire labeled X (3marks)
5. Now set up the circuit as shown in the figure below. Z is one of the 10 carbon resistors.

6. Close the switch. Tap the jockey at various points along the wire AB and locate a point P at which the galvanometer shows zero deflection. Measure and record in the table below the length ‘a’ where a = PB
7. Repeat the procedure in (f) using two resistors in parallel, three resistors in parallel, four resistors in parallel, five resistors in parallel, and six resistors in parallel. Record your readings in the table below. R is the effective resistance for the PARALLEL combination.
 Number of 10Ω resistors one two three four five six Effective resistance (R) length (a) in cm 1/R (Ω−1) 1/a (cm−1)
(5marks)
8. Plot a graph of I/a (y-axis) against I/R (5marks)
9. Determine the slope S, of the graph (2marks)
10. Given that I / a = β / kR + 1 / k, where k = 100cm, Use the graph to determine β   (2marks)

Question 2

PART A

1. You are provided with the following apparatus.
• A 50ml measuring cylinder
• A test tube
• About 200ml of Water in a 250ml beaker
• Six 1g ball bearings
• A vernier caliper
• Half meter rule
• Label
Procedure
2.
1.
1. Measure the internal diameter of the measuring cylinder using a vernier caliper.
D = ________________m (1 mark)
2. Calculate the area A of cross section of the inner part of the cylinder. (2 marks)
2.
1. Pour water into the measuring cylinder up to 50ml mark. Mark this point as h1 using the label.
2. Place the test tube upright inside the measuring cylinder so that it floats. Measure the increase in height of the water level from h1 using a half meter rule. Record this value in the table below.

3. Insert one ball bearing into the test tube then place the test tube back into the cylinder gently. NB (Remove the test tube slant it slightly and let the ball bearing roll to the bottom. Dropping the ball can break the test tube) measure the increase in height from h1
3.
1. Repeat the procedure in b(iii) above by adding ball bearings one by one each time measuring the new change in height H from h1. Enter the results in the table shown. (3 marks)
 Mass of ball (g) 0 1 2 3 4 5 6 Change in height (H) (cm)
2. Determine the weight of the water displaced Ww when the test tube has six ball bearings (density of water is 1 g/cm3) ( 3mks)
3. Determine the weight Wo of the test tube when empty given that
Ww = Wo + 0.06. (2 marks)
4. State any one source of error in the experiment above (1mark)

PART B

You are provided with the following:

• A bare copper wire with a loop on one end labeled W
• A retort stand, boss and clamp
• An optical pin mounted on a cork
• A stop watch
• A micrometer screw gauge to be shared
Proceed as follows:
1. Clamp the cork so that optical pin is horizontal. Hang the copper wire from the pin by the loop as shown in the figure below. Ensure the wire is straight and the length X between the lower tip and the optical pin is 20 cm.

2. Displace the lower tip of the wire slightly and then release it. Measure the time t for 10 oscillations of the wire and record the value in the table below.
3. Repeat the procedure in (b) above for two more trials each time recording the time taken in the table below. (3 marks)
 TRIALS 1 2 3 Time t for 10 oscillations (s) Period T = (s) T2 (S2)
4.
1. Determine the average of T2 to 4sf 1mark
2. Using a micrometer screw gauge, measure the diameter D of the wire in SI units (1mark)
3. Obtain the value of K in the equation T2 = 8π  (2marks)
3KD

CONFIDENTIAL

EACH STUDENT WILL BE PROVIDED WITH

Question 1

• Voltmeter (0 – 2.5V)
• Centre zero galvanometer
• Ammeter 0 – 1A
• A coiled resistant wire labeled X (nichrome wire SWG 30 of length 50cm )
• A resistance wire labeled AB mounted on a millimeter scale (nichrome wire SWG 32)
• 8 connecting wires each with crocodile clip at one end
• A switch
• A jockey/crocodile clip
• Six 10 ohms carbon resistors
• Two new size D dry cells
• Two cell holders of one cell each

Question 2

• A measuring cylinder of 50ml
• A test tube of mass between 12 - 15g
• About 200 ml of water in A 250ml beaker
• Six 1g ball bearings (From bicycle repairers)
• A vernier caliper
• Half meter rule
• Label
• A bare copper wire SWG 26 NB the wire should be 21 cm in length and a loop should be made on one end so that the final length of the wire is 20 cm
• A retort stand, boss and clamp
• An optical pin mounted on a cork
• A stop watch
• A micrometer screw gauge (to be shared)

MARKING SCHEME

QUESTION ONE

1.

(b) E= 1.5 ± 0.1 V 1mk      Award ½ mk if

No units, wrong units 0mk.

(c) I = 0.12 ± 0.02 A  1MK
V = 1.30 ± 0.1 V   1mk   Award ½ mk if
No units, wrong units 0mk.

(d) E = V + Ir and V = IR ,  Correct substitution from students values    1mk
CORRECT evaluation           1mk
Correct answers for r and R worked from students values with units Ω 1mk  Award ½ mk if
No units, wrong units 0mk.

(g)

 Number of 10Ω resistors one two three four five six Effective resistance (R) 10 5 3.333 2.5 2 1.667 length (a) in cm 45.0 31.5 25.0 20.0 18.0 14.0 1/R (Ω−1) 0.1 0.2 0.3 0.4 0.5 0.6 1/a (cm−1)

(h) Axis (1mk) both well labeled with units
Scale (1mk) simple and uniform
Plotting (2mks) each correctly plotted point within 1 small square
½ a mark a maximum of 4 pts
Line ( 1mk) a straight line through at least 4 correctly plotted pts

(i) Change in y ½ mk
Change in x ½ mk
Correct answer 1mk NB award ½ MARK FOR NO UNITS, NO MARK
FOR WRONG UNIT

(j) β/100 = S Correct substitution from students values 1mk
CORRECT evaluation (ignore units) 1mk

QUESTION 2 PART A

(a) i   D=2.90 ± 0.02 cm 2dp a must

ii  A= π(D/2)2 Correct substitution from students values 1mk
CORRECT evaluation 1mk

(c) i

 Mass of ball (g) 0 1 2 3 4 5 6 Change in height (H) (cm) 3 3.2 3.5 3.7 3.9 4.1 4.3

ii   V = A x 4.3
M = ρ x V
Ww = Mx10 Correct substitution from students values 1mk
CORRECT evaluation                                1mk
Correct answers for Ww worked from students values with units N 1mk Award ½ mk if
No units, wrong units 0mk.

iii  Ww = Wo + 0.06. Correct substitution from students values 1mk
CORRECT evaluation 1mk

iv  Water spillage
Inaccurate measurement

QUESTION 2 PART B

 TRIALS 1 2 3 Time t for 10 oscillations (s) 7.56 7.59 7.58 Period T = (s) T2 (S2)

Principle of averaging ½ mk
Correct evaluation ½ mk

D = measure the diameter of wire provided within 2 dp a must ½ mk
Conversion to SI units ½ mk 5dp a must

T2 =
3KD .     Correct substitution from students values 1mk
CORRECT evaluation 1mk

1 mks

2 mks

3mks

All correct 1mk
½ mk each ±0.1   1dp max 2mks

All correct 1mk

All correct  1mk

5mks

5mks

2mks

2mks

20 mks

1mk

2mks

½ mk each ± 0.1 1   dp max of 3mks

3mks

2mks

1mk

½ mk each ±1 s   2dp max of 1mk

All correct 1mk

All correct 1mk

3mks

1mk

1mk

2mks
20mks
40 mks

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