(i) Sketch a graph of reading on the voltmeter against I as the jockey is moved from point A to point B. (ii) State the readings on the voltmeter when the jockey is connected to A and when it is connected to B. (you may assume that the driver cell has negligible internal resistance.) (iii) Draw a circuit diagram to show how the potentiometer could be used to compare the e.m.f. of two batteries.

Solution:

(i)Straight line through origin with potential gradient. Graph axes labelled V (x-axis) and l (y-axis)

(ii) Readings on the voltmeter will be V=0 when jockey is connected to A as it is at null point. But readings on the voltmeter will be V=2 when jockey is connected to B as emf of cell represents the potential difference between two points.

(iii)