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1. Introduction

Electromagnetism is one of the four fundamental forces of the universe (the others are the strong nuclear force, the weak nuclear force, and gravity).

Electromagnetism deals with a wide range of physical phenomena, but at its core it is about the effects of electric and magnetic fields on charged particles and vice versa.

A "full" treatment requires knowledge of Einstein's Theory of Relativity. However, these simple cases are sufficient for this course.

Common electromagnetic phenomena include:

  • Electricity;
  • Light;
  • Radiant heat;
  • Radio;
  • The appearance (colour, lustre) of any given object;
  • Chemical bonding.

In fact, any phenomenon that's above the atomic scale, and is not gravity, is electromagnetic in one way, shape or form.

The picture below shows the electromagnetic spectrum. The rainbow inset shows the visible light spectrum.

Electromagnetic Spectrum


As you can see, electromagnetic waves have a wide variety of uses and effects, dependent on the frequency or wavelength.

Mains electricity is distributed at a frequency of 50 Hz.

Electromagnetic Fields

The electromagnetic phenomena are mediated by the electromagnetic field. This field appears as an electric field, a magnetic field, or a combination depending on your relative movement (in the sense of Einstein's Theory of Relativity). Fortunately, the effects of the electromagnetic field can be separated into separate electric and magnetic fields at the scales relevant to this course.

Electromagnetic fields propagate (or travel) through space.

The speed of light in a vacuum is exactly 299792458 m.s-1. In wires it is a little slower, but the wavelength of 50 Hz electricity is about 6000 km.

This is why we can "get away" with having separate electric and magnetic fields.

The importance of studying electromagnetism comes is for the following reasons:

  • charged particles generate electric fields;
  • moving charged particles generate magnetic fields;
  • time-varying magnetic fields generate electric fields;
  • time-varying electric fields generate magnetic fields;
  • electric fields exert forces on charged particles;
  • magnetic fields exert forces on moving charged particles.

Every one of those points creates a measurable phenomenon, and can be harnessed to transfer energy from one form to another.

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