CAIE IGCSE Physics 4.4.4 Why the outer casing of an electrical

Practise explaining why metal appliance cases need earthing while insulating or double-insulated cases do not need an earth wire.

Exam points

explain that an earthed metal case conducts fault current if the live wire touches it
distinguish a conducting outer case that must be earthed from an insulating double case
link earthing a kettle or transformer case to reducing electric shock risk

[Maximum number: 1]

Fig. 3.1 shows a mains electric heater used to heat a small room.

Fig. 3.1

The metal outer casing of the heater is earthed. State why this is an important safety feature.

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