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how can you avoid overloading?

The current flowing in domestic wiring at a particular time depends on the power ratings of the appliances being used. If too many electrical appliances of high power rating (like electric iron, water heater, air conditioner, etc) are switched on at the same time, they draw an extremely large current from the circuit. This is known as overloading the circuit. Overloading can also occur if too many appliances are connected to a single socket. Now, due to an extremely large current flowing through them, the copper wires of household wiring get heated to a very high temperature and a fire may be started.

It is also obvious that we should have some device which may disconnect the electricity supply when a short circuit or overloading occurs so that the electric fires are prevented in our homes. To avoid this danger of electric fires we use an electric fuse in  the wiring.

A fuse is a small  piece of thin wire of an alloy of lead and tin having high resistance and low melting point.

Fuses are safety devices which limit the value of the current that can pass through a circuit. For instance, the metal of the wire of a 5 A fuse is so manufactured that the fuse wire melts and breaks the circuit, if a current greater than 5 A flows through it. As a result fire hazards are avoided. The value of the fuse chosen for a particular circuit depends on the wire and appliances used in that circuit. The fuse wire is so designed  as to melt long before the wires in the circuit become hot enough to cause a fire. Thus, the heating effect of electric current is made use of in fuse. The rating of a fuse is the strength of the current  at which the fuse melts.