Lenz's law

Physicist Emil Lenz (pronounced ) formulated Lenz's law in 1834, after which it was named for him.

Magnetic fields
"The direction of current induced in a conductor by a changing magnetic field due to Faraday's law of induction will be such that it will create a field that opposes the change that produced it."

For current I that generates a magnetic field
 * $$B = L I$$

The induced current generated
 * $$-\phi = -NB = - N L I$$

Theoretical Lenz's law
Def. "a law of electromagnetic induction which states that an electromotive force, induced in a conductor, is always in such a direction that the current it would produce would oppose the change which caused it; it is a form of the law of conservation of energy" is called Lenz's law.