The secondary coil is also generating a magnetic field that is growing and shrinking just like the field in the primary coil. This coupling of magnetic energy between these two coils is called mutual induction.

A capacitor stores energy in the form of an electrostatic field between its plates. Increasing the size of the plates increases the capacitance because there is more room for the electrons to escape.

In a generator, a rotating magnetic field is used to produce electrical energy. When a conductor, such as a wire, moves through a magnetic field, a voltage is induced across the conductor. This is known as electromagnetic induction, and it is the fundamental principle behind how generators work.