Inductors

An inductor is a passive, two-terminal electrical component. When the current flows through the inductor, it stores energy in a magnetic field.

The inductor is made from an insulated wire wound on the core and makes a coil. Therefore, it is also known as coil, reactor, or choke.

Definition

An inductor is a coil or electromagnetic device that opposes any change in current. The design of an inductor (number of turns wound of a coil) depends on the application. An inductor is a conducting wire wound on an insulator.

The inductor is the name of a component and the value of it is called inductance.

When an electric current pass through the conductor, the magnetic field will generate around it. Let say, the current passes through the conductor are I, and the flux linkage is ф. The inductance is defined as the ratio of the flux linkage (ф) to the current passes through the conductor (I).

L = ф/I

Unit

Inductance is measured in Henry (H) or millihenry (mH) or microhenry (μH) and it is denoted by L. Letter (L) is used to denote the inductance i.e. linkages of magnetic flux and its unit is Henry.

Henry is a very large unit. Therefore, millihenry and microhenry are other small units used for inductors.

1 mH = 1 x 10^-3 H

1 μH = 1 x 10^-6 H

Construction and Symbol

The below figure-a shows the construction of an inductor and figure-b shows its symbol. It is a fixed value inductor.

N number of turns are wound around an iron Core. The material used to wound the coil is laminated copper wire.

Factors Affecting Inductance

The inductance of the coil depends on the following factors;

• The inductance increases when the number of turns increases. Because more voltage can be induced.
• If the area of each turn increases then the value of the inductance increases.
• Inductance depends on the permeability (g) of the core.
• If the length of the same number of turns increases then the dB value of inductance decreases.

Inductive Reactance

Reactance is the opposition presented by a pure coil to the flow of complex current through it. The reactance of the coil is called inductive reactance and is denoted by X_L.

X_L = 2πfL

Where  f = Frequency of applied EMF in hertz.

L = Inductance of the coil

This expression shows that the inductive reactance is zero for DC signal (zero frequency) and increases with an increase in frequency.