MAINS ELECTRICITY

2 marks · Normal

Explain how double insulation protects the user of a domestic electrical appliance.

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Also accept: Prevents the user from touching any electrical part; No need for earth wire because no metal casing is exposed

Common mistakes: Just says 'it is safer' with no reason

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Marking points

M1 · 1 mark · States that double insulation means two separate insulating layers.

A1 · 1 mark · Explains that this prevents the user from touching live parts or the case becoming live.

Worked solution

Double insulation means that both the wires and the casing are insulated. This prevents the user from ever touching any voltage-carrying part, so even if the internal insulation fails, the external casing remains safe.