Lenz’s law gives
the direction of induced emf and the direction of induced current (if circuit is closed).
Lenz law states that “The induced current will flow in such a direction
so as to oppose the cause that produces it”.
Lenz’s
law Explanation :-
Let us understand Lenz’s law from the
above figure. Here the N-pole of the magnet is approaching a coil of several turns. As the N-pole of the
magnet moves towards the coil, the magnetic flux linking the coil increases. Therefore,
an emf is induced in the coil according to the Faraday’s laws of
electromagnetic induction.
According to Lenz’s law, the direction of induced
current will be such as to oppose the cause that produces it. Here the cause of
induced current is the increasing magnetic flux linking the coil.
Therefore,
the induced current will set up magnetic flux that opposes the increase
in flux through the coil. This is possible only if the left hand face of
the
coil becomes N-pole.
Once we know the magnetic polarity of the coil face, the
direction of induced current can be easily determined by applying right hand
grip rule.
It may be directly noted here
that Lenz’s law directly follows from the law of conservation of energy.
In the above case, the coil
north pole (induced) will repel the incoming magnet north pole. Therefore,
mechanical work must be done in overcoming this repulsion and this work done is
actually converted into electrical energy which appers in the coil.
Thus Lenz’s law is consistent
with the law of conservation of energy.
