Inductors do not behave just like resistances. While the resistors simply oppose the flow of electrons through them (by lowering a voltage directly proportional to the current), the inductors resist the current changes through them, lowering a voltage directly proportional to the current change rate.

According to Lenz’s law, this induced voltage is always of such a polarity as to try to keep the current at its current value. That is, if the current is increasing in magnitude, the induced voltage will “push” against the electron flow; if the current is decreasing, the polarity will reverse and “push” with the electron flow to counteract the decrease. This opposition to current changes is called reactance, rather than resistance.

Mathematically expressed, the relationship between the voltage drop across the inductor and the current change rate through the inductor is as follows:

**e = L di/dt**

The expression di / dt is one of the calculation, ie the rate of change of instantaneous (i) current in time, in amperes per second. The inductance (L) is in Henrys, and the instantaneous voltage (e), of course, is in volts. Sometimes you will find the instantaneous voltage rate expressed as “v” instead of “e” (v = L di / dt), but it means exactly the same. To show what happens with AC, let’s look at a simple inductor circuit.

**IN SHORT**

An inductor is a passive electronic component that stores energy in the form of a magnetic field. In its simplest form, an inductor consists of a loop or wire coil. Inductance also depends on the bobbin radius and the type of material surrounding the bobbin.

They are used to block the AC, while allowing DC to pass; Inductors designed for this purpose are called “chokes”. They are also used in electronic filters to separate different frequency signals and, in combination with capacitors, to make adjustable circuits used to adjust radio and TV receivers.