Lenz's Law

From HvWiki

A useful law of electromagnetism that gives the direction of any induced force, magnetic field or current:

Induced current and its accompanying magnetic flux seek to oppose changes in flux through the circuit

Note that this law is only a handy way to remember the directions of effects. Magnitudes can be computed using Faraday's Law.

Examples of Lenz's Law

If you wave a strong magnet, such as a NIB, near a large conductor, it feels "syrupy". This is because any movement of the magnet induces currents in the conductor. By Lenz's law, it always induces currents with a magnetic field that tries to stop you moving the magnet.

Another example is the transformer. If you have two coils, with the same winding sense, a rising voltage (or current) on one winding will induce a falling voltage (current) in the other.