Live, neutral and earth
Three wires in a UK plug: live (brown, ), neutral (blue, ), earth (green/yellow).
Mains supply (UK). AC at .
The three wires.
| Wire | Colour (UK) | Voltage | Function |
|---|---|---|---|
| Live (L) | Brown | AC | Carries current TO the appliance |
| Neutral (N) | Blue | Return path back to supply | |
| Earth (E) | Green/yellow | Safety wire to ground |
Why earth? The earth wire connects the METAL CASING of an appliance to the ground. If the live wire becomes loose and touches the casing, current would flow through any person touching the casing β potentially fatal. Instead, the earth wire provides a low-resistance path to ground; a large current flows, blowing the fuse and disconnecting the supply.
Plug wiring rules.
- Brown to L (right side, looking at the plug from behind).
- Blue to N (left).
- Green/yellow to E (top).
- Cable grip clamps the OUTER sheath, not individual wires.
- Live (brown): .
- Neutral (blue): return.
- Earth (green/yellow): safety to ground.
- Cable grip on outer sheath.