Cracking the SAT Physics Subject Test

stationary circuit

The motion of the sliding rod through the magnetic field creates an electromotive
force, called motional emf:

ε = vBℓ

This relationship between current in a coil of wire and magnetic fields sets the
basis for an important law. Faraday’s Law states that there is a current in a coil or
loop of wire if and only if the magnetic field passing through the coil is changing.