Why the Earth Wire Saves Lives
🔌 Why the Earth Wire Saves Lives
UK three-pin plug — click each wire or component to see its function, colour code, and exam tips.
- 1Live wire (brown) —
- 2Neutral wire (blue) —
- 3Earth wire (green/yellow) —
- 4Fuse —
Figure 1: UK three-pin plug — click each wire or component to see its function, colour code, and exam tips.
Essential values (memorise these):
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Wire colours — "Brown Lives, Blue Neutral, Green-Yellow Earth":
Brown = Live (Be careful — it's Lethal!)
Blue = Neutral (think: bland/safe at 0 V)
Green/Yellow = Earth (think: grass and sun = the earth and ground)
Fuse selection rule — "Just Above, Never Below":
Calculate the normal current using I = P/V. Choose the fuse that is just above this value from the available options (3 A, 5 A, 13 A). Never choose one that's below — it would blow immediately. Never choose one that's much higher — it won't protect.
Earth wire purpose — "Earth Escapes, Fuse Finishes":
The Earth wire provides an escape route for fault current. The large current then causes the Fuse to Finish (melt), cutting the circuit.
Now try it yourself
Quiz · Question 1 of 18
What does AC stand for, and how does it differ from DC?
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This topic in real past papers
Every real exam question we've found on mains electricity & safety, with a full worked answer.