Lenz's law. Lenz’s law, in electromagnetism, statement that an induced electric current flows in a direction such that the current opposes the change that induced it. This law was deduced in 1834 by the Russian physicist Heinrich Friedrich Emil Lenz (1804–65).

Lenz’s law is based on Newton’s third law which is the law of action and response and the principle of conservation of energy. This is the best way to determine the path of an induced current. An induced electromagnetic field with different polarities creates a current whose magnetic fields reject the difference in magnetic flux through it.