# KCSE Past Papers 2020 Physics Paper 3 (232/3) Kenya Certiﬁcate of Secondary Education

Practical

2020 Physics paper 3

Question 1

You are provided with the following:

• Two cells in a cell holder;
• A switch;
• A micrometer screw gauge;
• A nichrome wire mounted on a millimetre scale;
• A voltmeter;
• An ammeter;
• A jockey:
• Connecting wires with crocodile clips.Proceed as follows:

Using the micrometer screw gauge, measure and record the diameter d of the wire.

d=……..mm

d=………m (1 mark)

Set up the apparatus as shown in Figure 1. Using the voltmeter, measure the potential difference E across the battery before closing the switch.

E = ……..volts. (1 mark)

Adjust the length L of the wire to 0.1m (10cm). Close the switch, read and record the value of the current I in Table 1.

Repeat (d) for the other values of L given in Table 1. Complete the table. (6 marks)

Length L (m) 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Current I (A)
Current I (A)

On the grid provided; plot the graph of 1/I (y axis) against L. (5 marks) • From the graph, determine the:

(ii) Intercept C on the 1/I axis. (1 mark)

h. Given that:

(i) 4K1/πd²E = S determine the value of K1

(ii) K1/E = C determine the value of K2

Question 2

You are provided with the following:

• A metre rule;
• A biconvex lens;
• Source of light (bulb in a bulb holder, cells in a cell holder and a switch);
• A stand boss and clamp;
• A lens holder;
• A screen;
• A half metre rule;
• Three pieces of plastic pipes A, B and C;
• A vernier callipers (to be shared);
• A stopwatch;
• Some plasticine.Proceed as follows PART A

(a) Clamp the bulb holder onto the stand. Arrange the bulb, the lens and the screen along the metre rule as shown in Figure 2.

• (b) Adjust the distance of the bulb from the lens to U = 25 cm. Put on the switch and adjust the position of the screen from the lens so that a sharp image of the bulb is observed.

Record the distance V between the screen and the lens in Table 2.

(c) Repeat part (b) for the other values of U shown in Table 2. Complete the table. (7 marks)

U cm 25 30 35
V cm
M = V/U
F=V/M+1

(d) Determine the average value of F.(2 Marks)

PART B (e) Using the vernier callipers measure and record the diameters of the three pipes.

dA, dB and dC

dA= ……….Cm……………… m

dB= ……….Cm……………… m

dC= ……….Cm……………… m

(f) Measure and record the thickness X of the half metre rule.

X= ………………..CM……………… m

(g) Place the pipe marked A on the bench and use the plasticine to stop it from rolling. (see Figure 3 (a) (i)   Push one end of the balanced half metre rule slightly downwards and release it so that it oscillates up and down. Measure and record in Table 3 the time for five complete oscillations.

(j)  Repeat the procedure in (g), (h) and (i) for the other‘ pipes B and C. Complete Table 3.(5 marks)

Pipe A Pipe B Pipe C
Diameter d (m)
Time for five oscillations Periodic time T (s)
Periodic Time T(S)
Ƶ= T√3(d – X)/2

(k) Determine the average value of Z (2 marks)

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