# Basics of Electromagnetism

by Ron Kurtus (revised 9 January 2019)

Electromagnetism has two meanings, depending on whether viewed at the subatomic level or on an everyday scale.

At the subatomic level, electromagnetism is defined as the force between electrically charged particles. It is considered one of the fundamental interactions of matter. Oscillating electrical charges result in electromagnetic waves.

On a larger scale, electromagnetism is the creation of a magnetic field from the movement of electrical charges. It usually concerns the use of electric current to make electromagnets, which is called electrodynamics. Another effect is electromagnetic induction, which is using an electromagnet or changing magnetic field to induce an electric current.

Questions you may have include:

• What is electromagnetism at the subatomic level?
• What is electrodynamics?
• What is electromagnetic induction?

This lesson will answer those questions. Useful tool: Units Conversion

## Electromagnetism at the subatomic level

At the subatomic level, electromagnetism is related to the electromagnetic force that causes the attraction and repulsion of electrically charged particles. It is considered one of the fundamental forces in nature, that also includes gravitational and nuclear forces.

When electrically charged particles, such as electrons, are put into motion, they create a magnetic field. When these particles are made to oscillate, they create electromagnetic radiation. This can include radio waves, visible light, or x-rays, depending on the frequency of the oscillation.

(See Electromagnetic Waves Overview for more information.)

## Electrodynamics

Electrodynamics is creating a magnetic field from an electric current.

When electricity passed through a wire, a magnetic field is created around the wire. Looping the wire increases the magnetic field. Adding an iron core greatly increases the effect and creates an electromagnet. You can also create an electromagnet without the iron core. That is usually called a solenoid.

### Magnetic field created from flowing electrons

When DC electricity is passed through a wire, a magnetic field rotates around the wire in a specific direction.

Magnetic field rotating around wire

### Right hand rule

To find the direction the magnetic field is going, you can use the "right-hand rule" to determine it. If you take your right hand and wrap it around the wire, with your thumb pointing in the direction of the electrical current (positive to negative), then your fingers are pointing in the direction of the magnetic field around the wire. Try it with the picture above.

You can also see the direction of the magnetic field by placing a compass near the wire.

### Wire in a coil

Wrapping the wire in a coil concentrates and increases the magnetic field, because the additive effect of each turn of the wire.

Coiled wire increases magnetic field

A coil of wire used to create a magnetic field is called a solenoid.

(See the lesson on Solenoids for more information.)

### Electromagnet

Wrapping the wire around an iron core greatly increases the magnetic field. If you put a nail in the coil in the drawing above, it would result in an electromagnet with the a north seeking pole on the "N" side.

(See the lesson on Electromagnets for more information.)

## Electromagnetic induction

Electromagnetic induction is creating an electric current from a changing magnetic field.

When a wire moves through a magnetic field, the electromagnetic effect takes place, creating an electric current through the wire.

Current created in wire moving through magnetic field

(See the lesson on Generating Electrical Current for more information.)

Likewise, when a changing magnetic field affects a metal wire, the current is changed. One application is to change the electrical voltage, through the use of a transformer.

(See the lesson on Alternating Current (AC) Transformers for more information.)

## Summary

At the subatomic level, electromagnetism is defined as the force between electrically charged particles. It is considered one of the fundamental interactions of matter. Oscillating electrical charges result in electromagnetic waves.

On a larger scale, electromagnetism usually concerns the use of electric current to make electromagnets. This is often called electrodynamics and is related to electromagnetic induction, which is using an electromagnet or changing magnetic field to induce an electric current.

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## Resources and references

Ron Kurtus' Credentials

### Websites

Electromagnetic Basics - Coilgun Systems

Electromagnetism - Wikipedia

Magnetism Resources

## Questions and comments

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electromagnetism.htm

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