Answer / rakesh

When an alternating potential difference is applied across
two conductors such that the spacing between the two is
large as comnpared to the spacing between the two , then an
electrostatic stress is set up , which gradually builds up
to make and makes the air around the conductor conducting ,
if he potential difference is increased to the extent that
exceeds the visual critical limit then comlete breakdown of
air takes place , and is accompanied by faint luminous glow
of violet colour , production of ozone gas , and hissing
noise .
DISADVANTAGES : 1. There is a definite los of power .
2. The corona current is non sinusoidal and hence causes
some disturbance to the neigbouring communication lines .
3. The ozone gas produced reacts with the conductor and
corrodes it .
ADVANTAGES : As the air becomes conducting so there is a
virtual increase in diameter of the conductor and henc
decreases the resistance.
2. It acts as a safety valve for neutralizing lightning
surges and overvoltages caused ddue to other transients .

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