Question 2
- Connect the circuit diagram as shown in Figure 2.
- Ask the supervisor to check the circuit connection.
- Copy Table 2 into your answer booklet.
Table 2
- Switch on the power supply unit.
- Set the power supply unit to 9V.
- Adjust the potentiometer to set the value of Ib to 100 µA.
- Read and record the corresponding values of Ic and VCE.
- Repeat steps (f) and (g) for the other values of Ib.
- Switch off the power supply unit.
- Comment briefly on the values of Ic against the values of Ib and VCE.
The candidates were expected to connect the circuit as shown, measure and record the values as indicated in Table 2. Interpretations and deductions were expected to be from the values recorded by respective candidates only.
Observation
The expected answers were:
-
Table 2
Ib (mA)Ic (mA)
VCE (V)
100
18.890
0.121
150
18.947
0.095
200
18.973
0.082
250
18.991
0.074
300
19.000
0.067
(j) (i) As Ib increases Ic remains constant.
(ii) As Ib increases VCE decreases.
Some of the candidates could not perform experiment 2 and a few were unable to make
proper deductions .