Electronics 3 Nov/Dec 2014

Electronics Paper 3, Nov/Dec 2014

Questions:	1	2	Main

General Comments
Weakness/Remedies
Strength

Question 1

AIM: To investigate the voltage divider rule.

Connect the circuit as shown in Figure 1.
Ask the Supervisor to check the circuit connections.
Copy Table 1 into your answer booklet.

Table 1

Vin(V)	V1(V)	V2(V)	V3(V)
2
4
6
8
10

Close switch S and set the input voltage Vin to 2 V.
Read and record in Table 1 the values of V1, V2 and V3.
Repeat step (e) for the other values of Vin in Table 1.
Open switch S.
Using the values in Table 1 plot graphs of:

(i) V2 on the vertical axis against V1 on the horizontal axis;
(ii) V3 on the vertical axis against V1 on the horizontal axis.

Determine the slope of the graphs in (h)(i) and (h)(ii).
Compare the ratio with the slope of the graph in (h)(i).

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OBSERVATION

The candidates were expected to connect the circuit as shown, measure and record the voltmeter readings, plot the graphs of voltages against each other, determine the slopes of the graphs and do some comparison.
The expected answers were
(c)                                                      Table 1

Vin(V)	V1(V)	V2(V)	V3(V)
2	1.04	0.73	0.22
4	2.09	1.47	0.45
6	3.13	2.20	0.67
8	4.18	2.93	0.89
10	5.22	3.67	1.11

(j)      Comparison: The voltage divides in direct proportion to the values of R2
     and R1.

The Chief Examiner reported that the many candidates showed good knowledge of components’ connection but were inadequate in the given answers.