Question

WHAT IS THE FUNCTION OF EARTH WIRE ?WHY IS IT NECESSARY TO EARTH METALLIC APPLIANCES

Answer 1

the earth wire is used to protect the user from any accidents that occurs using a metal applications.if there is any problem in the application the case itself becomes live with the possibility of electrocuting anyone who then touches the case. discharge any stray charge on the body,if earthing is not done then it will shock if touched.Without the earth wire, you can get a shock.  an Earthed wire, permanently connected to the case  will provide an immediate path for current to safely flow through .. so the case remains safe to touch.

The metal is connected to the earth wire  any leakage of electric current is transferred to the ground through the earth wire. This prevents severe electric shock to the user. That is why earthing of the electrical appliances is necessary.
Being a low resistance path, the Earth connection lets a large current flow through it when the fault occurs .. this ensures that the plug fuse will quickly 'blow' .. breaking the circuit to the mains to complete the safety measures.

Answer 2

The main function of the earth wire is to conduct the leaking current  from the electrical appliance to the ground . It is conected to the outer metallic body of the appliance .

It is necessary to earth metallic appliances , as it protects the user from electric shocks by transferring the current to the earth.