Electronics Paper 3, Nov/Dec 2014
 Questions: 1 2 Main
Weakness/Remedies
Strength

Question 2

AIM: To investigate the current divider rule.

1. Connect the circuit as shown in figure 2.
2. Ask the supervisor to check the circuit connection.

Table 2

 Vin(V) I1(mA) I2(mA) I3(mA) 2 4 6 8 10
1.  Close switch S and set Vin to 2 V.
2.   Read and record in Table 2 the values I1, I2 and I3.
3.   Repeat step (e) for the other values of Vin in Table 2.
4.   Open switch S.
5.   Using the values in Table 2, plot graphs of:

(i)  I2 on the vertical axis against I1 on the horizontal axis;
(ii) I3 on the vertical axis against I1 on the horizontal axis.

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

The candidates were expected to connect the circuit as shown, measure and record the ammeter readings, plot the graphs of currents against each other, determine the slopes of the graphs and do some comparison.
(c)                                                        Table 2

 Vin(V) I1(mA) I2(mA) I3(mA) 2 0.37 0.53 1.74 4 0.74 1.05 3.47 6 1.11 1.58 5.21 8 1.48 2.11 6.95 10 1.85 2.63 8.69

(j)      Comparison: The current divides in inverse proportion to the values of R1
and R3.

As reported by the Chief Examiner, the readings obtained by many of the candidates that answered this question showed that they did not know how to adjust meter settings to correspond to indicated values of measured quantities.