Question

Show that lenz law is in accordance with the law of conservation of energy

Answer 1

When we bring opposite poles of two magnets together, they attract each other (or vice versa). Now, we can say that the kinetic energy gained by the magnets is due to the attractive force.

Similarly, we say in Lenz's law that if the north pole of magnet is moved towards a solenoid (for example) then the north of the magnetic field produced by the induced current will be towards the north of the magnet to oppose the change in magnetic flux.

The explanation we give for the above (2nd paragraph) phenomena is the law of conservation of energy. Now, suppose that the opposition is not offered in the above phenomena and the south of the magnetic field produced by the induced current is towards the north pole of magnet. The motion of the magnet will be enhanced in this case and the magnitude of change of magnetic flux will increase. This is said to be the violation of law of conservation of energy. My question is that why is this violation of energy? if two opposite poles of magnet can attract each other why not the south of magnetic field of induced current and north of the magnet?

I know its a complicated question but that's is the best i could do with it. I will appreciate if anyone could edit it to make it better but don't change the question.

Answer 2

Hey !!

LENZ'S LAW :- According to this law ''the direction of induced current in a closed circuit is always such as to oppose the cause that produces it''

EXAMPLE :- When the north pole is brought near a closed coil, the direction of current induced in the coil is such as to oppose the approach of north pole. For this the nearer face of coil behaves as north pole. This necessitates an anticlockwise current in the coil.

                Similarly when north pole of the magnet is moved away from the coil, the direction of current in the coil will be such as to attract the magnet. For this the nearer face of coil behaves as south pole. This necessitates a clockwise current in the coil.

 CONSERVATION OF ENERGY IN LENZ'S LAW

Thus, in each case whenever there is a relative motion between a coil and the magnet. a force begins to act which opposes the relative motion. Therefore, to maintain the relative motion, a mechanical work must be done. This work appears in the form of electric energy of the coil.

           Thus, law is based on principle of conservation of energy.

HOPE IT HELPS YOU !!