Question 3A
You are provided with a variable d.c. power supply E, a 2 Ω standard resistor, a key, an ammeter, a voltmeter and other necessary materials.
(i) Set-up a circuit as shown in the diagram above with E = 1.5 V.
(ii) Close the key K.
(iii) Take and record the voltmeter reading V.
(iv) Take and record the corresponding ammeter reading I.
(v) Evaluate V-1 and I-1.
(vi) Repeat the procedure for four other values of E = 3.0 V, 4.5 V, 6.0 V and 7.5 V.
(vii) Tabulate your readings.
(viii) Plot a graph with V-1 on the vertical axis and I-1 on the horizontal axis starting both axes from the origin (0, 0).
(ix) Determine the slope, s, of the graph.
(x) Also determine the intercept, c, on the vertical results.
Observation
Part (a) This was a fairly popular question among the candidates. Many candidates attempted the question and performed well in the trend of V and I. However, many did not record the value of E on the table and hence V and I cannot be scored because of trend. Also, candidates lost marks in V-1 and I-1 due to inconsistencies in significant figures/decimal places and the inability to choose good scale for graph.