Inductors or Coils

An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy.

Any conductor of electric current (any wire for that matter) has inductive properties and can be seen as an ‘inductor’ and in order to enhance the ‘inductive effect’, a practical inductor is usually formed into a cylindrical coil with many turns of conducting wire.


The voltage across an inductor is zero when the current is constant. In other words: An inductor acts like a short circuit for DC!

For the DC current, the coil acts as a piece of wire with a very low (almost zero) resitance. For AC current the coil acts as a resistor, combined with a capacitor.

An inductor is a component that can store energy in the form of a magnetic field. Another way to look at inductors is that they are components that will generate a magnetic field when current is passed through them, or will generate an electrical current in the presence of a changing magnetic field.

To explain exactly why inductors work the way they do is quiet complex – keep that in mind. Imagine a straight piece of wire (see below) -if we pass a current through, a circulair magnetic field is formed around it.

If we would bend this piece of wire, it shows that each side of the loop has fields in opposing directions. This is what creates our north- and south-pole on a electromagnet.

If we would add more loops we actually increase the number of magnetic rings being generated by the wire and therefore make a more powerful eletromagnet. In other words, we increased its inductance.

If we have a coil with no current flowing through it – the coil does nothing really. If we now would move a magnet through it, the changing magnetic field induces a current into the coil.

An example how the amount of inductance (measured in Henry [H]) can be calculated:

Coil with a ‘core’


A more common coil/inductor that we use is the ‘guitar-pickup’ for example. This pickup-coil consists of a permanent magnetic core inside the coil. By moving a string nearby the core of the pickup, a current is induced. See the picture below:

Guitar pickup


If you want to ‘move’ or ‘acuate’ an object, then a solenoid can be very practical to use. A solenoid is a coil (inductor) with a moveable iron core. If current is flowing through the coil, the iron core will be pushed out (or pushed in). See the picture below.


If the current stops flowing, the spring will push back the core. A practical application is opening the lock of doors for example.

* With thanks for the images and some tekst content: