IIT JEE , AIEEE Forum - Physics , Magnetism -

master_purav

Suppose a magnet is moving in direction of a circular coil. As the magnet approaches the coil, the flux linked with it constantly increases. Thus emf is induced.

Now the direction of this emf is decided on basis of Lenz Law.

Suppose a North pole of magnet is brought towards coil. Assume that the induced current is in Clockwise direction in the coil. Consequently it will behave as South pole. Thus magnet is attracted towards the coil and moves with more and more velocity inducing more current and making south pole stronger and stronger. Thus magnet would move with infinite velocity.

Here no energy is given to the magnet other than a slight push. Rest energy is given by the coil's attraction. Thus we get infinite electric energy by just a liitle mechanical energy input. Thus it voilates Law of Energy conservation.

So the current cannot flow in clockwise direction. Thus it will flow in Anti clockwise direction.

Hence the coil behaves as North Pole. In this case induced field will try to repel the magnet. Hence work must be done against this induced field. This work is converted to Energy. Thus Law of Energy conservation is not violated.

Hope u r clear now...........

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