Inductor and Inductance | Inductor Fundamentals

An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy. Basically, it uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction.

Inductor concept

The more turns with which the conductor is wound around the core, the stronger the magnetic field that is generated.

A strong magnetic field is also generated by increasing the cross-sectional area of the inductor or by changing the core of the inductor.

Inductor Circuit Symbol

The circuit symbol for an inductor indicates the coil nature of the inductor. There are several formats indicating whether the inductor or transformer has a air core or a magnetic core.

circuit symbol of inductor


Inductance is a property of an electrical circuit or component that describes its ability to store energy in a magnetic field when an electric current flows through it.

It is typically denoted by the symbol “L” and is measured in henrys (H). Inductance is a fundamental concept in electromagnetism and is a key parameter in the behavior of electronic components such as inductors and transformers.

When current flows through a conductor, it creates a magnetic field around it. The magnetic field induces a voltage in the same conductor or nearby conductors. This phenomenon is known as electromagnetic induction. Inductance quantifies the amount of magnetic flux generated for a given amount of current.

The formula that relates inductance, voltage, and current is given by Faraday’s law of electromagnetic induction:

V = L\frac{{di}}{{dt}}

V = L\frac{{di}}{{dt}}


  • V is the induced voltage,
  • L is the inductance,
  • di/dt is the rate of change of current with respect to time.

When indicating an inductor on a circuit diagram or within an equation, generally the symbol “L” is used. On circuit diagrams, inductors are generally numbered, L1, L2, etc.

Self Inductance

Self-inductance can be defined as:

  • The phenomenon in which a change in electric current in a circuit produces an induced electro-motive-force in the same circuit.

In terms of the units the following self-induction definition may be applied:

  • The self-inductance of a coil is said to be one henry if a current change of one ampere per second through a circuit produces an electro-motive force of one volt in the circuit.

Mutual Inductance of Two Coils

When the emf is induced into an adjacent coil situated within the same magnetic field, the emf is said to be induced magnetically, inductively or byMutual induction, symbol ( M ).

Then when two or more coils are magnetically linked together by a common magnetic flux they are said to have the property ofMutual Inductance.

Inductive Reactance

Inductive reactance is the opposition offered by the inductor to the flow of electric current through it. OR The effect by which the current flow of an alternating or changing current in an inductor is reduced is called its inductive reactance.

Inductive reactance equations

When a changing signal such as a sine wave is applied to a perfect inductor, i.e. one with no resistance, the reactance impedes the flow of current, and follows Ohms law.

{X_L} = \frac{V}{I}

XL = inductive reactance on ohms, Ω
V = voltage in volts
I = current in amps

The inductive reactance of an inductor is dependent upon its inductance as well as the frequency that is applied.

{X_L} = 2\pi fl

XL = inductive reactance on ohms, Ω
π = Greek letter Pi, 3.142
f = frequency in Hz
L = inductance in Henries

Q Factor

The quality factor (orQ) of an inductor is the ratio of its inductive reactance to its resistance at a given frequency, and is a measure of its efficiency. The higher the Q factor of the inductor, the closer it approaches the behavior of an ideal, lossless, inductor.

The Q factor of an inductor can be found through the following formula, whereRis its internal (Series Model) electrical resistance and is the inductive reactance at resonance:

Q = \frac{{\omega L}}{R}

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