Electromagnetism

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What is electromagnetism?

The term electromagnetism refers to the effect of a magnetic field forming around every current-carrying conductor. Electric current, therefore, generates a magnetic field.
Electromagnetism includes all phenomena that can be attributed to electricity or magnetism. Alongside atomic forces and gravity, the electromagnetic force is a fundamental physical force. Today, it is known that almost all phenomena in our environment, except for Earth’s gravity, are based on electromagnetism. Accordingly, they can be described by electrodynamics.

Table of Contents

Electromagnetism is a term encompassing the totality of electrical and magnetic phenomena. In physics, electromagnetism refers to a standardised understanding of electricity and magnetism. The theory of electromagnetism in physics is electrodynamics.

The discovery of electromagnetism

For a long time, no clear distinction was made in physics between electrical and magnetic forces. This either led to confusion between the two phenomena, or researchers saw no connection at all between electricity and magnetism.

It was not until 1820 that Oersted recognised that a current-carrying conductor exerts a magnetic force on a nearby compass needle and thus established that a magnetic field emanates from moving charges. James Clerk Maxwell formulated Maxwell's equations in 1864, thereby developing the mathematical foundations of electrodynamics for a standardised description of electromagnetism.

Find out more about the history of magnets in our guide.

The basics of electromagnetism

Electric charges are the sources of electric fields. Magnetic fields are created by currents, i.e. moving charges, and time-varying electric fields, which in turn are also created by time-varying magnetic fields.

Charged objects exert electrical forces on each other. There are positive and negative electrical charges. Equally charged bodies (i.e. both negatively or both positively charged) repel each other and differently charged bodies (one negative, one positive) attract each other. It has been established that the forces disappear when the charges flow away. This can happen, for example, through contact with grounded metal parts or simply by touching the charged objects, although this can result in an electric shock.

In magnets, a force acts even though the objects are not charged. The force effect does not disappear when the objects are grounded or touched. This is because magnetic forces are caused by the movement of electrons in the magnetic material. The charge motion takes place at the individual atoms of the magnetic material, and there is no excess charge that can flow away somewhere.

Moving charges, without exception, generate magnetic forces. This always creates a magnetic field with a north pole and a south pole. There are no sources of the magnetic field in the same way that charges are the sources of the electric field. When an electromagnet is generated, a strong current is sent through a coil, creating a strong magnetic force.

Many phenomena of electromagnetism, such as the existence of electromagnetic waves, can be predicted and calculated with Maxwell's equations.

Electromagnetism as an explanation for forces and phenomena in everyday life

In addition to electromagnetism and the associated forces, the only other fundamental physical forces are gravity and nuclear forces. All phenomena in our world can be explained by these forces. It is remarkable that almost all forces and phenomena that we observe in everyday life are electromagnetic in nature. Only the forces of atomic energy are noticeable nuclear forces, and Earth’s attraction of objects as well as the movement of stars, planets and moons in the celestial firmament are phenomena of gravitation.

Electrodynamics covers the theories of magnetism and electricity in their entirety. It is astonishing how electrodynamics is used in physics to explain a wide variety of phenomena that are initially not clearly recognisable as electrical or magnetic phenomena.

The stability of matter itself is mainly explained by electromagnetism. In atoms, negatively charged electrons orbit the positively charged atomic nucleus.

Hardness, colour, lustre, shape, thermal conductivity and many other properties of matter can be explained by electromagnetic forces. All measurable energy radiation in our environment (except particle radiation) are electromagnetic waves such as radio waves, mobile phone radiation, microwaves, thermal radiation, light radiation and X-rays. They differ only in their different wavelengths.

If a few material parameters are known, the colour, the electrical conductivity, the reflection on the surface, the light transmission of a material or the refraction of light on the surface can be precisely calculated. This applies not only to light but also to radio waves, X-rays and all other electromagnetic waves.

A basic understanding of electromagnetism is, therefore, not only helpful in the development of electronic circuits but can also explain a wide variety of phenomena in our environment.

Author:
Dr Franz-Josef Schmitt

Dr Franz-Josef Schmitt is a physicist and academic director of the advanced practicum in physics at Martin Luther University Halle-Wittenberg. He worked at the Technical University from 2011-2019, heading various teaching projects and the chemistry project laboratory. His research focus is time-resolved fluorescence spectroscopy in biologically active macromolecules. He is also the Managing Director of Sensoik Technologies GmbH.

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