A railway-crossing warning unit contains two resistor branches connected between the same two points of a 12 V supply. The current measurements before a switch is opened are shown.
| Branch | Current before the switch is opened |
|---|---|
| A | 0.18 A |
| B | 0.27 A |
The switch is then opened so that branch B is disconnected. The supply potential difference remains 12 V, and branch A remains a complete circuit.
Calculate the current from the supply before the switch is opened.
Explain what happens to the total resistance of the circuit when branch B is disconnected.
94 exam-style questions on AQA GCSE Physics 2.2 Series and parallel circuits, covering 2.2 Series and parallel circuits. Each one has a worked solution and a mark scheme showing where the marks go.