Electrical Safety

Electricity can be dangerous if used incorrectly. Safety features like fuses, circuit breakers, and earthing protect people and appliances from damage. Understanding why we use these features helps prevent accidents at home and at school.

Why Electrical Safety Matters

Too much current can:

overheat wires and start fires
give you an electric shock, which can be fatal
damage appliances

Safety Features

Fuses

A fuse is a thin wire inside a small casing. It melts if the current becomes too large, breaking the circuit.

If a fault causes 15 A to flow through a circuit protected by a 5 A fuse, the fuse melts → circuit breaks → no more current → safe.

Always replace a fuse with one of the correct rating (same or just above the normal working current).

Circuit Breakers

A circuit breaker is a switch that automatically trips (opens) when too much current flows. Unlike a fuse, it can be reset by flipping the switch back.

Earthing

The earth wire (green/yellow) provides a low-resistance path to the ground. If a fault causes the metal casing of an appliance to become live, the earth wire allows current to flow safely to the ground, tripping the fuse.

Insulation

Wires are covered in plastic insulation which does not conduct electricity. This prevents you from touching live metal.

Warning

Never: touch electrical sockets with wet hands, use damaged cables, overload sockets (too many plugs), or try to fix electrical problems yourself unless qualified.

Three-Pin Plug Wiring

Wire	Colour	Function
Live	Brown	Carries current to appliance
Neutral	Blue	Completes the circuit back to supply
Earth	Green/Yellow	Safety — carries fault current to ground

Real world: Washing machine earth wire

A washing machine has a metal drum and casing that are connected to the earth wire (green/yellow). If a wiring fault inside makes the casing live, current immediately flows through the earth wire to ground instead of through a person touching the machine — this trips the fuse and prevents electrocution.

Real world: RCD (Residual Current Device) in modern homes

Modern homes and electrical installations include an RCD (also called RCCB or GFCI). It detects tiny differences in current between the live and neutral wires (as small as 30 mA) that indicate current is leaking through a person. It trips within 30 ms — far faster than a fuse — making it the most effective protection against fatal electric shock.

Real world: Why you must not use appliances in the bath

Water (especially with dissolved salts from skin) is a conductor. Wet hands have a resistance around 1,000 Ω instead of the usual 100,000 Ω of dry skin. By Ohm's Law (I = V/R), a 230 V supply with 1,000 Ω resistance would drive 230 mA through the body — ten times the fatal threshold of ~25 mA. This is why electrical sockets are banned inside bathrooms.

Tip Where do you see this in real life? Every plug socket has insulation, fuses protect every circuit, and the earth wire in your appliances is literally a lifesaver — electrical safety features are built into everything!

Practice Problems

What does a fuse do, and when does it act?

Show answer

A fuse melts and breaks the circuit when the current exceeds its rating (e.g. a 3 A fuse breaks when more than 3 A flows). This protects the circuit from overheating.

What is the advantage of a circuit breaker over a fuse?

Show answer

A circuit breaker can be reset (switched back on) after it trips. A fuse must be replaced because the wire inside melts.

Which wire in a 3-pin plug is brown?

Show answer

The live wire is brown. It carries current from the supply to the appliance.