Faraday's Law ties all of our observations into one neat package. It says that the emf induced in a coil of N turns is given by the rate of change of the magnetic flux in the coil:

Faraday's Law:

e

=

– N

DFB Dt

This has an incredible number of practical applications, particularly in the generation and distribution of electricity.

We call the voltage induced by a changing magnetic flux an induced emf. This is because changing magnetic flux acts like a battery in a coil or loop, which is why there is a current when there's a complete circuit.

What is this emf thing anyway? It stands for electromotive force, and has units of volts. The voltage of a battery is often called the battery emf, so the ideas here is that changing the magnetic flux through a loop or coil makes the loop or coil act like it has a battery in it.