Question

earthing is effective only when there is a fuse explain
18 points

Answer 1

Fuses are typically to protect wiring and other components from overheating and perhaps catching fire and/or exploding in the event of a low-impedance fault. From the Wikipedia article "Fuse (electrical)":

A fuse interrupts an excessive current so that further damage by overheating or fire is prevented. Wiring regulations often define a maximum fuse current rating for particular circuits. Overcurrent protection devices are essential in electrical systems to limit threats to human life and property damage.

However, one could easily be electrocuted without tripping a breaker or blowing a fuse. Thus, earthing a metal appliance, enclosure, plumbing, etc. prevents potentially lethal voltages from developing on these conductors.

Answer 2

To avoid the risk of electric shocks , the metal body of an electrical appliances is earthed.
Earthing means to connect the metal case of electrical appliances to earth at zero potential by means of earth wire.

In house hold circuits , we have three wires, the live wire, the neutral wire and earth wire.
One end of earth wire is buried in earth.
we connect the earth wire to metal casing of electrical appliances by using three pin plug.
If by chance, live wire touches any metal case parts of appliances then current passes directly to earth.
hence earthing is used as safety measure to prevent shock from metal objects.

The fuse breaks the circuit if a fault in an appliance causes too much current flow. This protects the wiring and the appliance if something goes wrong. The fuse contains a piece of wire that melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.

#Fuses are not designed to prevent electric shock. ... You will note that the earth wire is not there to limit the current through the live wire rather it is there to have a current flow through the live wire which is large enough to blow the fuse and so disconnect the live wire from the device.#


hope it helps you.....