A bridge circuit has two parallel branches connected across a cell. One branch contains resistors X X\,X and Y Y\,Y in series, with X X\,X connected to the positive terminal and Y Y\,Y to the negative terminal. The other branch contains resistor Z Z\,Z and a light-dependent resistor W W\,W in series, with Z Z\,Z connected to the positive terminal and W W\,W to the negative terminal. A voltmeter is connected between the junction of X X\,X and Y Y\,Y and the junction of Z Z\,Z and WWW.
Initially, the voltmeter reads zero. The resistance of W W\,W then increases, 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
a reduction in the resistance of YYY
an increase in the resistance of ZZZ
an increase in the resistance of XXX
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.