Question 2

AIM: Determination of the equivalent resistance of a circuit.

(a) Connect the circuit as shown in Figure 2.
(b) Ask the supervisor to check the circuit connection.
(c) Copy Table 2 into your answer booklet.

Table 2

Power supply voltage Vs(V)	V(V)	I(mA)
4
6
8
10
12

(d) Set the power supply to 0 V.
(e) Close switch S.
(f) Adjust the power supply to 4 V.
(g) Read and record the ammeter and voltmeter readings in Table 2.
(h) Repeat steps (f) and (g) for other power supply voltages shown in Table 2.
(i) Plot the graph of V(V) on the vertical axis against I(mA) on the horizontal axis.
(j) Determine the slope of the graph.
(k) Comment on the slope of the graph

The candidates were expected to connect the circuit as shown in Fig.2, measure and record in Table 2 the voltmeter and ammeter readings. They were also required to plot a graph of voltage V(V) against current I(A) and comment on the slope of the graph.

The expected answers were:
Table 2
(c)

Power supply voltage Vs(V)	V(V)	I(mA)
4	1.7	1.0
6	2.4	1.5
8	3.3	2.0
10	4.1	2.4
12	5.0	2.9

(j) The slope of the graph was 1.71 kΩ.

Candidates’ performance in this question was better than that of Question 1. The voltage and current readings obtained and the graph plotted compared favourably with those provided in the marking scheme.