# Physics Paper 3 Questions and Answers - MECS Cluster Joint Mock Examinations 2022

QUESTIONS

QUESTION 1

You are provided with the following:

• 2 new dry cells size D.
• A cell holder.
• A switch.
• An ammeter (0 – 1A)
• A voltmeter (0 – 5V)
• 6 connecting wires, 3 with crocodile clips.
• Nichrome wire mounted on the metre rule labelled X.
• A micrometer screw gauge (to be shared).

Proceed as follows:

1. Connect the circuit as shown in the figure below. 2. Measure the voltage, E before closing the switch.
E = …………………………………………(1mk)
3. Adjust the length L of the wire 0.2m, close the switch S and read the value of current and record in the table below.
4. Repeat the procedure in (c) above for the value of length, L and fill the table for 1/I . (5mks)
 Length L(m) 0.2 0.3 0.4 0.5 0.6 0.7 Current I(A) 0.6 0.52 0.44 0.4 0.35 0.29 1/l(A-1)
5. On the grid provided plot a graph of 1/I (y axis) against L. (5mks)
6. Determine the gradient of the graph.  (3mks)
7.
1. Measure the diameter of the wire in three points using micrometer screw gauge. (1mk)
d1 = ………………
d2 = ………………
d3 = ………………
Averaged d = …………………………………………….…..      (1mk)
2. Determine the cross-section area, A of the wire.   (1mk)
8. From the equation 1/I = KL/AE + Q/E determine;
1. the value of K. (2mks)
2. the value of Q.(1mk)

QUESTION 2
PART A

1. You are provided with the following:
Triangular glass prism
Four optical pins                            Thermometer
250 ml beaker                                Plain paper
Soft board                                      Stopwatch
source of boiling water                  Four office pins

Proceed as follows

1. Fix the plain paper on the soft board using the office pins.
2. On the plain paper, draw line XY. Mark a point M on its midpoint. Draw a normal N at M to XY. Draw line RM such that angle RMN = 50°.
(This paper will be collected at the end of the experiment) (1mk) 3. Place the glass prism such that one edge AB of the prism is in line with XY. Accurately draw the outline ABC of the prism
4. Place optical pins P1 and P2 on the line RM
5. Through edge BC observe the images of P1 and P2. Fix P3 and P4 so that P1, P2, P3 and P4 lie on straight line.
6. Remove the pins; construct straight line from P4 through P3 to meet side BC at D, join M to D.
1. Measure angle r1. (1mk)
r1 = ………………………………..
2. Produce P4P3 to meet RM produced. Measure angle d.  1mk)
d………………………………..
3. Draw the normal at D and measure the angle r2. (1mk)
r2 ……………………………….
7. Given that R= r1+ r2. Calculate R  (1mk)
8. Given that n= sin⁡(R+d/2), find the value of n.(3mks)
sin⁡(R/2)
9. Given that n sin⁡k=1, find the value of k (2mks)
10. What Physical property does n represent?  (1mk)

PART B
(Read all the instruction before starting this part)

1.
1. Using the thermometer, measure and record the temperature of the room, θ.
θ………………………………………………℃.(1mk)
2. Using the 250 ml beaker, collect 200 ml of hot water from the boiling source. Place the thermometer into the hot water and wait until it cools to 80 ℃ the start the stopwatch and record time t1 it takes to cool to 75℃.
t1 …………………………………. seconds. (1mk)
3. Wait until the water cools to 70 ℃ and then start the stopwatch and record the time t2 it takes the water to cool to 65 ℃
t2   ………………………………….. seconds.  (1mk)
2. Determine the rate of temperature change ρ and β in the two intervals.
1. ρ=77.5-θ/t1 (2mks)
2. β=67.5-θ/t2(2mks)
3. State with reason how the rate of change of temperature between 50 ℃ and 45 ℃ compares with ρ(2mks)

CONFIDENTIAL
QUESTION 1

You are provided with:

• Two new dry cells (size D).
• A cell holder.
• An ammeter (0 – 2.5A) OR (0 – 1A)
• A voltmeter (0 – 5V)
• connecting wires 2 with crocodile clips.
• Nichrome wire 1.0m long mounted on a scale (SWG 28) labelled X.
• A micrometer screw gauge (to be shared)

Each student should have the following:

• Four optical pins
• Alcohol Thermometer
• 250 ml beaker
• Plain paper (A4 size)
• Soft board
• Stopwatch
• Source of boiling water
• Four thumb tucks
• Equilateral triangular glass prism
• Complete geometrical set ## MARKING SCHEME

1. E = 3.0V (1mk)

2.  Length L(m) 0.2 0.3 0.4 0.5 0.6 0.7 Current I(A) 0.6 0.52 0.44 0.4 0.35 0.29 1/l(A-1) 1.667 1.923 2.273 2.5 2.857 3.448
Correct values each ½mk max 3mks
Correct values 1/l  ½mk max 3mks
3. Graph
• Axes well labeled with unit. (1mk)
• Scale simple uniform and easy to plot (1mk)
• Plotting 6 points (2mks)
5 points (1mk)
Less than 4 no mark
ΔL(m)
= 2.5 - 1.67(1mk)
0.5 - 0.2
= 0.83
0.3
= 2.767Aˉ¹mˉ¹  (1mk)
5.
1. dave = 0.38mm (1mk)
2. χ - section Area A = 22/7 (1.9 x 10-4)² = 1.134 x 10-7m² (1mk)
6. From the equation
1/l = K/AE(L) + Q/E
But E = 2.9V,  A = 1.134 x 10-7
K = 2.767 x 1.134 x 10-7 x 2.9
= 9.10 x 10-7Ωm (1mk)
Q/E Intercept = 1.08Aˉ¹
Q = 1.08Aˉ¹ x 2.9
= 3.132(1mk)

QUESTION 2
Part A

1.
1. r1 =28°  (Penalize □(1/2)mk for unit not given i.e degrees in all  angles)   (1mk)
2. d =37° (1mk)
3. r2 =30° (1mk)
2. R=28°+ 30°(Correct substitution =   1/2mk)
=58°  (Correct evaluation =   1/2mk)
3. n=sin⁡(58+37/2  (Correct substitution =  1mk)
sin⁡(58/2)
sin⁡47.5/sin⁡29 (Correct evaluation =  1mk)
n=1.521 (unitless 4sf=1mk)
4. n sin⁡k=1
1.521sin⁡k=1 (Correct substitution =  1mk)
sink=1/1.521
k⁡=sin-11/1.521
=41.11°  (Correct evaluation =  1mk)
5. Refractive index of glass (1mk)

Part B

1.
1. θ = 19.5   (17- 27)℃  (1mk)
2. t1  = 110.46 s
3. t2  = 175.85 s
2. ρ= 77.5-θ/t1
=77.5-19.5/110.46
=0.5251⁄s  (Correct evaluation =  1mk)
β=67.5-θ/t2
=67.5-19.5/175.85   (Correct substitution =  1mk)
=0.2730⁄s (Correct evaluation =  1mk)
3. The rate of change of temperature will be lower than ρ. (1mk)
Rate of cooling decreases with decrease in temperature difference. (1mk)

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