Question

What is the name for what is basically an induction coil whereby the voltage of an alternating current can be increased or decreased without changing the frequency?

Answer 1

A transformer is a type of induction coil that can step up voltage or decrease it without affecting the AC frequency.

For example: If we have two mutually connected inductive coils and we energize one coil with AC, we will create an AC voltage in the other coil. When used as such, this device is known as a transformer.