WHAT IS AN INDUCTOR?

In the electronic field we hear the terms Inductor, Inductance and Inductive Reactance. What are they?

A thorough explanation would take a 2 year college course. However, knowing the basics can be of value.

An inductor and magnetism are closely related.

An electric current will produce a magnetic field. This field is more pronounced when the current is going through a wire. If you have one, you have the other.

A magnetic field in motion, crossing a wire, will generate an electric current in the wire. The basic idea for an electric generator.

To make the magnetic field stronger with an electric current, you form a coil with the wire. This way every time the current goes around a winding it makes a magnetic field. Then it goes around the next winding and the next adding to the strength of the magnetic field.

You can observe this if you wind a thin insulated wire (20 gauge) around a steel nail several times. Then connect a 1.5 volt battery to the winding. The nail will become magnetized with a North pole on one side and a South pole on the other. You have just made an inductor.

Putting a steady direct current through an inductor will produce a steady magnetic field. What will happen when the electric current changes? A lot.

When you first connected the battery to the coil, for a quick instant the magnetic field was increasing. You could not detect it this way, but by building magnetic strength, an electric current was produced in the opposite direction, produced from the magnetic field building and crossing the wire coil. When you disconnect the electric current, it happens again.

This electric current induced in the opposite direction, opposes the current you initially put into the coil. This gives the affect of having resistance in the circuit.

To be able to detect this, you can put an alternating current into the coil. The continuously changing current will cause an opposite flowing current with every change. This will cause the current applied to the coil to reduce. This resistance is called Inductive Reactance (X_L). It is measured in ohms just like a resistor.

How much resistance will it produce?

It will depend on the design of the coil. It can be very little resistance, or enough resistance to almost completely cut off the current. A power transformer is an example of the latter.

Connecting a power transformer to a high voltage like 120 volts, with no load on the transformer, will draw very little current. However, if you measure the resistance across the transformer winding, it will only measure a few ohms. If you connect a direct current to the transformer, the current will go very high and most likely burn out the transformer.

There is much more to an Inductor and this will be in future articles.

73,

Ralph WD0EJA

05/16