MAINS ELECTRICITY

2 marks · Normal

Explain why it is dangerous if the earth wire in a metal-cased appliance is disconnected.

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Also accept: If the live wire touches the casing and the earth wire is missing, current may pass through a person instead of the earth, causing electric shock.

Common mistakes: Just says 'it is dangerous' without explanation

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Marking points

M1 · 1 mark · States that if the live wire touches the casing, there is no low-resistance path to earth.

A1 · 1 mark · Explains that a person touching the case could get an electric shock because current could flow through them.

Worked solution

If the earth wire is disconnected and the live wire touches the metal casing, there is no safe path for current to flow to earth. As a result, a person touching the casing may receive an electric shock.