difference of 240V. The minimum and maximum limit of current that can be drawn from the mains is 5 – 20A. Thus, the maximum current that we can draw from the mains is 20A. When the current drawn from the mains is more than 20A. Overheating< occurs and may cause a fire. This is called over loading. See figure 32. If we switch on devices, such as heater shown in figure 32, the current drawn from the mains exceeds the max limit 20A.


• How can we prevent damage due to overloading?

To prevent damages due to overloading we connect an electric fuse to the household circuit as shown in figure 32.

In this arrangement, the entire current from the mains must pass through the fuse.

The fuse consists of a thin wire of low melting point.

When the current in the fuse exceeds 20A, the wire will heat up and melt.

The circuit then becomes open and prevents the flow of current into the household circuit.

So all the electric devices are saved from damage that could be caused by overload.

     Thus we can save the house holding wiring and devices by using fuses.
     Note: The value of overload current varies from the household currents to factories.