We have seen that moving charges and currents produce a magnetic field around them. In 1830 Michael Faraday and Joseph performing independent experiments and they demonstrated that changing magnetic fields produce electric field and electric current. The induction of electric field and electric current by changing magnetic field is called electromagnetic induction.
Electromagnetic induction is very phenomenon which is responsible for the development of modern day generator and transformers.Let we see about Lenz’s laws of electromagnetic induction.Lenz's law electromagnetic induction:According to Lenz’s law “the direction of induced current in a closed circuit is always such as to oppose the cause that produces it.”When the north pole of a magnet is taking near a blocked coil, the route of current provoked in the coil is for instance to contest the approach of North Pole (source:wikipedia).
For this the nearer face of coil behaves as North Pole. This necessitates an anticlockwise current in the coil, when seen from the magnet side.From the below figure we can understand this concept.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, when seen from the magnet side.From the below figure we can understand this concept.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 coil. Thus Lenz’s law is based on conservation of energy.From the above concepts we can easily understood the Lenz's law of electromagnetic induction.