Category: Practical Electricity

A live wire carries a high voltage and carries current from the electrical plug to the appliance.

The switch connected to the live wire will ensure that the appliance is at zero voltage every time the appliance is switched off, making the appliance safer to use.

The fuse connected to the live wire will ensure that high current flow to the appliance will immediately be cut off, preventing damage to the wirings and appliance due to the high current flow.

This appliance is missing an earth wire, but it most likely has double insulation.

Appliances with double insulation have their internal parts and wirings completely insulated from the outer casing, and the outer casing will be made of an electrical insulator, eg plastic.

This means that, even if a live wire touches the casing, it will not become “live”, hence it will be safe to use even without an earth wire.

Note: Appliances with double insulation will have this symbol:

The live wire is at high voltage, and carries the current from the electrical mains to the electrical appliance. If any electric fault occurs, resulting in high current flow, the fuse/switch/circuit breaker on the live wire will immediately cut off the high current/high voltage before the high current/voltage can cause damage to the electrical wirings and the appliance.

The live wire is at high potential difference, while the neutral wire is at zero potential difference. When the switch is turned off, the electrical appliance will still be at high voltage, since the electrical appliance is still connected to the electrical mains via the live wire.

The electrical appliance being ‘live’ even though the switch is turned off is potentially hazardous as it increases the risk of electrocution and overheating and electric fire if a path to a lower potential difference is established.

When current that is higher than the fuse rating flows through the circuit, the wire in the fuse melts and breaks the circuit.

This will prevent the high current from flowing through the wirings and the electrical appliance, preventing overheating of the wires, and damage to the appliance.