A metal-cased laboratory water bath is connected to the 230 V mains supply. A 3 A fuse is fitted in its live wire.
A fault causes the live wire to touch the metal case. A technician services the earth connection. The table gives the total resistance of the circuit carrying current through the fuse when the fault is present.
| Test | Total circuit resistance in Ω\OmegaΩ |
|---|---|
| before maintenance | 92 |
| after maintenance | 0.46 |
Calculate the current through the fuse in each test.
Explain how the maintenance changes what happens when the fault occurs.
81 exam-style questions on Edexcel GCSE Physics 10.4 Mains electricity, covering 10.4.1 Direct and alternating current, 10.4.2 Live, neutral and earth wires; safety, 10.4.3 Mains wire potential differences and dangers, and 10.4.4 Power ratings and energy use. Each one has a worked solution and a mark scheme showing where the marks go.