Paper 3 DC Circuits Drills

Q1 Fault diagnosis

A lamp and resistor are connected in series to a cell. A voltmeter across the lamp reads zero, while a voltmeter across the resistor reads the full supply p.d. The lamp is dark.

1. Suggest the likely fault. [2]
2. Explain the voltmeter readings. [3]
3. State how the readings would differ if the lamp were open-circuit instead. [3]
4. Explain why an ideal voltmeter has high resistance. [2]

Q2 Brightness comparison

Three identical lamps are connected to the same ideal battery. Circuit A has one lamp alone. Circuit B has two lamps in series. Circuit C has two lamps in parallel.

1. Rank the brightness of each lamp in A, B and C. [3]
2. Explain using power. [4]
3. State what happens to total current drawn from the battery in C compared with A. [2]