The candidates were expected to connect the circuit as shown in Fig.1, measure and record in Table 1 current readings, plot the graph f(Hz) versus I(mA), determine the resonant frequency and the associated current from the graph.
The expected answers were:
Table 1
Number of cells |
V(V) |
I (mA) |
L(condition of bulbs) |
2 |
3.0 |
80.00 |
OFF |
3 |
4.5 |
120.00 |
DIM/DULL |
4 |
5.9 |
160.00 |
BRIGHT |
5 |
7.4 |
200.00 |
BRIGHTER |
6 |
8.7 |
240.00 |
BRIGHTEST |
(k)The slope of the graph was 36.6 ?.
(l) The resistance of the bulb was 12.2 ?.
The candidates, as reported, were able to obtain the readings and plot the graph. However, many of them got the voltage readings in this question wrong.