Your house has a circuit
Show on a big screenA house has three wires, and each has its own job. The meter counts the electricity the house uses.
- The supply enters through a meter, on live and neutral wires.
- A fuse sits on the live wire, near the meter.
- Lamps sit in parallel, each with its own branch.
- An earth wire joins the metal body of an appliance.
The rule
A house has live, neutral and earth wires. The fuse goes on the live wire. Appliances are joined in parallel. In normal use the earth wire carries no current. It carries current when there is a fault. A fault is a failure. One example is the live wire touching a metal body.
Mains current can kill. Only a trained electrician works on real wiring. This lesson uses drawings only.
| Wire | Job |
|---|---|
| Live | Brings the supply in. The fuse sits on it. |
| Neutral | Takes the current back to the supply. |
| Earth | Joins the metal body of an appliance to the ground. |
A fuse is a thin wire. The fuse melts when too much current flows. That breaks the circuit, and the current stops. Overloading is drawing too much current from one circuit. A short circuit is live and neutral touching directly.
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Worked example
A 1000 W heater runs on 220 V. Here P is the power in watts (W). V is the voltage in volts (V). Voltage drives the current. I is the current in amperes (A).
The heater's current is I = P ÷ V = 1000 ÷ 220, about 4.5 A.
A fuse must be rated a little above the current. A 5 A fuse suits it. The current, 4.5 A, is under 5 A. A 2 A fuse would melt at once. The current is over 2 A.
Suppose the live wire touches the heater's metal body. The earth wire carries the current to the ground. The heater's body stays at about the same voltage as the ground. A person who touches it is far less likely to be shocked.
Try the lab to finish this lesson.