9702/51/M/J/19: A student is investigating a rotary variable resistor, as shown in Fig. 2.1. The variable resistor is connected to a battery of electromotive force (e.m.f.) E and negligible internal resistance, as shown in Fig. 2.2.
The student uses a protractor to measure the angle θ through which the spindle of the variable resistor is rotated and records the current I. The experiment is repeated for different angles. It is suggested that I and θ are related by the equation E = IKθ where K is a constant.
