Inductor Energy Storage Calculator

Created by Wojciech Sas, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Oct 04, 2019

Are you wondering what this inductor energy storage calculator can do? Well, it estimates the energy stored in an inductor when an electric current is passing through it. We also provide the equation for the magnetic energy in the solenoid, and where this energy equation comes from. Further in the text, you'll also find a useful piece of information about how this phenomenon in used in practice.

What is the energy stored in an inductor

A solenoid is one of the most common electronic components. Solenoids have the ability to generate magnetic fields, and the ease with which the solenoid can create this field is known as its inductance. It's important to know that this magnetic field is present only if there is a current flow through the coil. Interestingly, the magnetic field accumulates a portion of energy, which can be released (or absorbed) whenever the value of the current changes. That's the reason why an inductor is a source of impedance in an AC circuits.

Magnetic energy stored in a coil formula

Assuming we have an electrical circuit containing a power source and a solenoid of inductance L, we can write the equation of magnetic energy, E, stored in the inductor as:

E = 1/2 * L * I²,

where I is the current flowing through the wire.

In other words, we can say that this energy is equal to the work done by the power source to create such a magnetic field.

As we can see, the energy stored in an inductor depends on the current to the second power. This tells us that the solenoid prevents a sudden current surge in the circuit, and that's the reason why we can see a spark when unplugging some electronic devices.

How to use the inductor energy storage calculator?

Let's say we have a circuit containing a power source and a coil of inductance L = 20 μH. We are looking for the energy stored in the inductor when we pass a direct current of I = 300 mA through the system.

  1. In case you don't want to mess up with your units, let's write all the values using scientific notation: L = 2·10⁻⁵ H, I = 3·10⁻¹ A
  2. Use the formula for magnetic energy in the solenoid: E = 1/2 * 2·10⁻⁵ H * (3·10⁻¹ A)² = 9·10⁻⁷ J
  3. The energy stored in the inductor can also be written as E = 0.9 μJ or 900 nJ
  4. You can always use this inductor energy storage calculator to make sure your result is correct!

Sometimes we may need to have more energy stored for our application. One thing we can do is to increase the inductance by adding a material with a high permeability, like ferromagnetic cores.

Applications of magnetic energy storage

One of the main uses of this stored magnetic energy is in LC circuits (containing both inductance and capacitance). In these cases, the energy stored in the inductor is transformed into the electrical energy of the capacitor, and vice versa. The system can be set to send and receive radio signals when the current oscillations reach the resonant frequency of the radio waves.

Inductors are also widely used in transformers, which change the amplitude of voltage from one circuit to another. The magnetic energy from one coil is carried to the second one via a soft ferromagnetic medium. Thanks to that, we have comfortable and safe access to electricity in our cities and homes.

Wojciech Sas, PhD candidate
Inductance (L)
Current (I)
Stored energy (E)
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