Question

Explain, with the aid of a circuit diagram, the method a student could use to investigate how the resistance of a single lamp changes with the potential difference across the lamp. [6 makrs]

Answer 1

Indeed, the resistance of the lamp changes with the temperature of the lamp. The higher voltage causes a higher current, the current heats the spiral inside the lamp. Therefore, we can use the following scheme: connect a voltage source, ammeter, and the lamp in series as shown in the figure:

Record ammeter readings every time as we change the value of voltage. The resistance of the lamp at given values of voltage and current is voltage divided by this current:

$$R_i=\frac{V_i}{I_i}.$$