Inductors in practice

An inductor is an elec- tronic component that possesses appreciable in- ductance. Self-inductance is the property of a circuit to oppose any changes in current flowing through the circuit: this manifests itself by the production of a voltage that tends to op- pose the change of cur- rent. This voltage is called the back-e.m.f. Mutual in- ductance is the phenomenon whereby voltage is induced in one circuit by changing the current in another. The unit of both self- and mutual inductance is the same: the henry, but their respec- tive symbols are L and M (or L12). An inductor has an inductance of 1 henry if the back-e.m.f. in it is 1 volt, when the current through it is changing at the rate of 1 ampere per second. Inductors invariably consist of many turns of wire wound adjacent to one another on the same sup- port, called the former, but in high-frequency appli- cations they are often self- supporting (i.e., air-cored). The former may also be of ferromagnetic material to increase the...