LENZ’S Law – The Direction of Induced E.M.F:
The direction of the induced e.m.f. is given by the Russian Scientist Lenz.
The direction of the induced e.m.f. is such that it opposes the cause producing the change of flux.
Induced e.m.f.\(E=\frac{d\theta }{dt}\). This equation is called Faraday’s law of induction or Neumann’s law.
The negative sign is put to show that the current due to the induced e.m.f. produces an opposing flux-change.
Explanation:
In North Pole of a magnet is shown approaching the end of a coil. If Lenz’s law is correct then the induced current must flow in a direction which makes the coil behave like a magnet with North Pole at the top face. Then the downward motion of the north pole of the magnet will be opposed by the force of repulsion exerted by the north pole of the coil. When the B magnet is withdrawn from the coil, the induced current flows in the opposite direction and the top face A of the coil becomes a south pole. Since unlike poles attract, the removal of the magnet is opposed.
Lenz’s law is an example of law of conservation of energy. The mechanical work done in moving the magnet against the opposing forces, is converted into electrical energy.