A cell is connected across two parallel branches. One branch contains resistors R1 R_1\,R1 and R2 R_2\,R2 in series, with R1 R_1\,R1 connected to the positive terminal and R2 R_2\,R2 to the negative terminal. The other branch contains a thermistor of resistance RT R_T\,RT and a resistor R3 R_3\,R3 in series, with the thermistor connected to the positive terminal and R3 R_3\,R3 to the negative terminal. A voltmeter is connected between the junction of R1 R_1\,R1 and R2 R_2\,R2 and the junction of the thermistor and R3R_3R3.
Initially, the voltmeter reads zero. The thermistor is then heated, causing its resistance to decrease while the other resistances remain unchanged.
Which change to the circuit will restore the voltmeter reading to zero?
An increase in the emf of the cell
An increase in the resistance of R1R_1R1
A decrease in the resistance of R2R_2R2
A decrease in the resistance of R3R_3R3
36 exam-style questions on AQA A Level Physics Current electricity, covering Basics of electricity, Current-voltage characteristics, Resistivity, Circuits, Potential divider, and Electromotive force and internal resistance. Each one has a worked solution and a mark scheme showing where the marks go.