The candidates were expected to connect the circuit as shown, measure and record the values of IB and IC, plot a graph of IC (mA) against IB(mA), determine and comment on the slope.
The expected answers were:
(f)
R (k?) |
IC(mA) |
IB(µA) |
220 |
7.26 |
23.00 |
330 |
4.88 |
15.00 |
470 |
3.42 |
11.00 |
560 |
2.85 |
8.00 |
820 |
1.92 |
6.22 |
Note: Range of values IB min. = 6.4 µA, IB max = 23 µA
for Exp. 2 IC min = 0.64 mA, IC max = 6.9 mA
(j) Slope of graph: Range of values of β is (100 – 350)
(k) Comment on slopes
Slope
β =
Both graphs are linear and the slopes are positive. is a linear constant.
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.