Inductor definition, symbol, unit, energy stored, formula, types & applications

Here I am talking about Inductor definition, symbol, unit, energy stored, formula, types, and applications.

What is an Inductor’s Definition?

Definition of the inductor may be in many ways:

By Definition, the inductor is an electrical/electronic circuit component that reflects some amount of resistance and inductance to the circuit.

It is a helical path of the conductor wounding on a certain core. The core may be air or any other material. Due to the conductor present in the inductor, the wire has some resistance as well. As soon as the inductor connects to the circuit it reflects resistance and inductance both. But resistance is very low (in mili-ohm).

As the inductor reflects inductance, its S.I unit is Henry (H). It is a very large quantity so it is in milli-Henry (mH).

An inductor is also a passive element. This means it only absorbs electrical energy and cannot deliver energy. It absorbs electrical energy and converts it into a magnetic field around it.

What is the Impedance of the Inductor?

Impedance has an SI unit of the ohm. Impedance is the combined output of the Resistance and Reactance. its symbol is ‘L’.

Z= \sqrt{R^{2}+  {X_{L}} ^{2}  }

Where, R: Resistance, XL: inductive reactance, Z: impedance.

Can I use AC or DC as a source for the inductor?

The inductor is an element that works on electromagnetic induction.

According to electromagnetic induction, voltage produces flux and vice a versa.

When the source is connected across Inductor, it produces a magnetic field or magnetic flux. By the formula of the voltage across it, “voltage is directly proportional to the rate of change of current through it.”

V=L \frac{di}{dt}

Where, L: inductance.

Explanation to DC as a source for inductor!

So, if the rate of change of the current is zero (means constant current: DC current) then the voltage across the inductor is zero. That means DC cannot be used across an inductor.

Alternatively, I can say, the inductor has some impedance as defined above. Impedance containing symbol XL which is inductive reactance .this depends upon the frequency of the supply.

X_{L} =2 \times  \Pi  \times  f_{L}

Where, f: frequency, L: inductance

But DC has zero frequency hence inductor will have impedance (Z)= (R) Resistance. This means a purely resistive network. Think then about why we connected the inductor. We should connect Resistor only if we need impedance equal to the resistance. That is a mistake. In this case, it will not produce flux. Hence DC cannot be used as a source.

Explanation to AC as a source for inductor!

If AC is a source, the inductor works properly. Because AC has time-varying voltage and currents. This gives the ok result to the above-explained voltage equation.

Alternatively, by the above formula of inductive reactance (XL) frequency is not zero in AC. It is generally 50Hz or any. Hence AC can be used as an inductor as a source.


  • Filter.
  • Choke coil.
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  • Solenoid.
  • And more.

A solenoid definition

The solenoid is also an inductor that absorbs electrical energy and releases it in the form of a magnetic field. The solenoid is a coil wound on a certain core that produces a magnetic field around it when connected to the source. Again, as it is an inductor also it needs time-varying current and voltages to work on. hence it cannot be connected to the DC source, It is connected to the AC.

As it produces a magnetic field, it is an example of the Electromagnet. When subjected to the electricity it produces flux around it.

Solenoid as Inductor

The direction of the magnetic field around the electromagnet/Solenoid is Magnetic North to Magnetic south(outside the core). Whereas Magnetic South to Magnetic north inside the core.

Noman zahoor

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