what is earthing?

Question Posted / manjot

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what is earthing?..

Answer / manjot

Earthing is a safety device used to prevent a shock due to
leakages arising from weak insulation, breaking of the
element or otherwise. The metal bodies of appliances handled
like the electric iron, kettle or refrigerator must be
earthed, that is, connected to a pipe leading deep into the
earth on to a metal plate. In case the metal body becomes
live, the circuit is completed through the live wire and the
earth, resulting in a high current. The fuse on the
live-wire side should blow out immediately, and the matter
should be investigated and the fault rectified. In case the
fuse does not blow out, and a person touches it, a severe
shock is still prevented. This is because most of the
current flows directly to the earth via the earth connection
which has negligible resistance. An extremely small current,
if at all, may pass through the person’s body which offers a
resistance, resulting in only a mild shock.
For an earth connection, a three-pin socket and plug are
required. Due to the high current it draws, the earth pin is
made thicker and larger than the other two pins. This
ensures that the plug fits firmly into the socket, reducing
the chances of sparking. The heat caused by sparking causes
the terminals to wear off and damages the socket and the
plug. Because it is larger, the earth connection is made
first acting as a safety device.