A control unit contains two fixed resistors, M and N, and a switch with a test position and an operating position.
In the test position, the resistors are connected in series. The readings are shown in the table.
| Supply potential difference (V) | Current (A) | Potential difference across M (V) |
|---|---|---|
| 6.0 | 0.20 | 2.0 |
In the operating position, the switch reconnects M and N as separate parallel branches across the same supply. The readings are taken before the temperature of either resistor changes, so their resistances have the same values in both positions.
Calculate the reading on an ammeter in the main branch when the switch is in the operating position.
Explain why the main-branch ammeter reading is greater in the operating position than in the test position.
81 exam-style questions on Edexcel GCSE Physics 10.2 Resistance, covering 10.2.1 Current in a circuit and conservation at junctions, 10.2.2 Resistance and variable resistors, 10.2.3 Series and parallel resistance, 10.2.4 I–V characteristics of components, and 10.2.5 LDRs and thermistors. Each one has a worked solution and a mark scheme showing where the marks go.