インダクタ

An inductor is a two-terminal circuit element consisting of coils of wire. Because of the current flowing in the circuit, magnetic flux passes through the inductor.

When there is a change in the current passing through the inductor, according to Faraday's law, a back emf is generated. This field is the magnetically induced non-conservative electric field.

Since the non-conservative field is nonzero only within the inductor, its integral around the whole loop can be replaced by its integral from one terminal to the other.

Hence, free electrons are accumulated on one of the inductor's terminals to produce a nonzero conservative electric field.

The total electric field is the sum of these two electric fields. If the inductor has negligible resistance, a test charge experiences no force inside. Hence, the total electric field within the coils must be zero. Thus, the non-conservative electric field in this integral can be replaced by the negative of the conservative electric field.

This integral is the potential difference between the terminals of the inductor, which is given by this formula.