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Effects of lightning strikes >
Direct effects 
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Thermal effects:
These effects are linked to the
amount of charge associated with
lightning strikes. They result
in fusion points melting holes
of varying sizes at the point of
impact of materials with high
resistivity. For material which
is a poor conductor, a large
amount of energy is released in
the form of heat. The heating of
water vapour contained in the
material results in very high
abrupt localized pressure which
may cause it to explode. |
Effects due to the initiation :
In the event of a lightning
strike a large increase in the
ground potential of the
installation will occur
depending upon the grounding
network and soil resistivity.
Potential differences will also
be created between various metal
elements. Hence the need to pay
particular attention when
installing earth rods and
inter-connection of metal
structures adjoining the
conductors. |
Acoustic effects -
thunder: Thunder is due to the
sudden increase in pressure (2
to 3 atmospheres) of the
discharge channel developed by
the electrodynamic forces during
the lightning flash. The
duration of a thunder clap
depends on the length of the
ionized channel. For high
frequencies, propagation of the
spectral components released by
the shock wave is perpendicular
to the channel. For low
frequencies, propagation is
omnidirectional; hence the
different forms of rumbling or
claps heard by an observer
depending on the distance and
orientation of the successive
channels used by the lightning
flash. |
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Luminous effects :
A lightning strike nearby
violently sensitizes the retina
of an observer. The eye is
dazzled and vision is lost for
several long seconds. |
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Electrodynamic effects :
Electrodynamic effects between
conductors and other parts occur due
to large magnetic field of the
lightning current.. This results in
substantial mechanical forces, both
attractive and repulsive, that are
all the stronger when the conductors
are close together or the current is
high.
Electrochemical effects : The
fleeting nature of lightning impacts (compared to stray ground currents) mean
that these effects are highly negligible and without influence on earth rods.
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