What Is Inductance?

In electrical and electronic circuits, inductance is a critical characteristic. This is a simple electrical measurement that, like resistance and capacitance, influences all circuits to some extent. Inductance is employed in a variety of electrical and electronic circuits and systems. Components come in a variety of shapes and sizes and are known by several names: coils, inductors, chokes, transformers, and so on. Each of these may come in a number of forms, including those with and without cores, as well as different sorts of core materials.

Understanding inductance, as well as the many types and formats of inductors and transformers, aids in comprehending what is going on in electrical and electronic circuits. Oliver Heaviside originated the word inductance in 1886. After the scientist Heinrich Lenz, the sign L is used for inductors represented on circuit diagrams and inductance in equations.

Inductance basics

The capacity of an inductor to store energy in the magnetic field formed by the flow of electrical current is known as inductance. The magnetic field requires energy to set up, and this energy must be released when the field collapses. Inductors create an opposing voltage proportionate to the rate of change in current in a circuit as a result of the magnetic field associated with the current flow. The magnetic field created by electric currents passing through an electrical circuit causes inductance. Typically, wire coils are utilised as a coil improves the magnetic field coupling and therefore the effect.

Inductance can be utilized in two different ways: Self-inductance is a property of a circuit, most often a coil, in which a change in current induces a change in voltage in that circuit owing to the magnetic influence of the current flow. Self-inductance is an inductance that applies to a single circuit, or in other words, it is an inductance that occurs within a single coil.

In single coils or chokes, this effect is employed. Mutual inductance is an inductive phenomenon in which a change in current in one circuit produces a change in voltage across a second circuit due to a magnetic field connecting the two circuits. Transformers make use of this effect.

Inductance unit definition

The sign “L” is commonly used to represent an inductor on a circuit diagram or in an equation. Inductors are usually labelled L1, L2, etc. on circuit diagrams. The henry, H, is the SI unit of inductance, which may be expressed in terms of current and voltage rate of change. The henry’s definition is as follows: If the rate of change of current in a circuit is one ampere per second and the electromotive force is one volt, the inductance of the circuit is one henry. 1 Wb/A is equivalent to one henry.


When current travels through a conductor, whether straight or in the shape of a coil, a magnetic field forms around it, which influences how the current flows once the circuit is completed. In order to understand how inductance impacts an electrical circuit, consider how the circuit works first with a direct current and then with an alternating current. Although they follow the same rules and have the same consequences, the direct current example is easier to understand, and this explanation can then be applied to the alternating current instance.

Direct Current

The current begins to flow as soon as the circuit is completed. The magnetic field produced by increasing the current to its constant value grows up to its ultimate form. Because the magnetic field is changing while this happens, Lenz’s Law predicts that a voltage will be induced back into the coil. L/R can be used to determine the circuit’s time constant T in seconds, which includes the inductor value L Henries and the associated circuit resistance R Ohms. T is the time it takes for the current I amps to reach 0.63 of its ultimate steady-state V/R value. The magnetic field stores 1/2 L I2 of energy. When the current is turned off, the circuit’s resistance effectively climbs to infinity in a matter of seconds. As a result, the L/R ratio becomes extremely tiny, and the magnetic field rapidly decreases.

As a result of the huge shift in magnetic field, the inductance strives to keep the current flowing while a back EMF is created to counteract it, originating from the energy stored in the magnetic field. Sparks might occur across the switch contact due to the voltages, especially when the contact is damaged. Pitted contacts and wear on mechanical switches result as a result of this. Back EMF in electrical circuits can harm semiconductor devices, hence methods to reduce back EMF are frequently used.

Alternating Current

The same basic concepts apply to alternating current traveling through an inductor, however, because the waveform is repeating, we choose to look at the inductor’s response in a slightly different way because it is more convenient. An alternating waveform is always changing by its very nature. This means that the resulting magnetic field will always change, and an induced back EMF will always be produced. As a result of this, the inductor obstructs the passage of alternating current through it due to its inductance. This is in addition to the resistance imposed by the wire’s Ohmic resistance.

Learn more about: A small square loop of wire of side l is placed inside a large square loop of wire of side L(Lgtgtl). The loops are co-planer and their centres coincide. The mutual inductance of the system is proportional to?

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