A shop has two refrigerated display cabinets, C and D, with metal cases. Each cabinet has a working, correctly rated fuse in its live wire.
In both cabinets, a damaged live wire touches the metal case.
An electrician finds that the fuse in C has melted. The fuse in D has not melted, and the case of D is still live.
Which is the most likely explanation?
C's earth wire is broken, but D's earth wire is connected to its case.
C's earth wire is connected to its case, but D's earth wire is broken.
Both earth wires are broken, and C's fuse melted because its case became live.
Both earth wires are connected, and D's earth wire safely carries the fault current.
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.