A law of electromagnetism which states that, whenever there is an induced electromotive force (emf) in a conductor, it is always in such a direction that the current it would produce would oppose the change which causes the induced emf. If the change is the motion of a conductor through a magnetic field, the induced current must be in such a direction as to produce a force opposing the motion. If the change causing the emf is a change of flux threading a coil, the induced current must produce a flux in such a direction as to oppose the change. Lenz's law is a form of the law of conservation of energy, since it states that a change cannot propagate itself. See Conservation of energy, Electromagnetic induction
a law on the direction of induced currents, that is, currents arising as a result of electromagnetic induction. Lenz’s law is a consequence of the law of the conservation of energy.
Formulated in 1833 by H. F. E. Lenz, the law states that an induced current arising in a closed circuit is so directed that the magnetic induction flux created by the current and passing through the circuit tends to oppose the change in flux that causes the given current. Thus, for example, the induced current in a loop placed in a magnetic field B, which is directed perpendicularly to the plane of the coil and away from the observer, will have a counterclockwise direction if the field increases with time and a clockwise direction if the field decreases with time.