Essay: electromagnetic pollution


The discovery that Electricity and magnetism are manifestations of the same basic entity, electromagnetism, was a great unification in physics. Unifications are very interesting, because they allow for explaining phenomena using a smaller number of theories.

Ideally, all physics will be unified one day. That has always been of the most ambitious targets of physics.

Other important example of unification was realized by Newton, with the law of gravity. Newton showed that falling objects on the Earth surface and celestial bodies are governed by the same laws. That means that he unified all mechanics in the Universe, he placed terrestrial and celestial movements under the same laws.


Electricity (Intro)


Charging by contact or friction and charging by induction

Electrodynamics: Electric current

Electric energy

Difference between static electricity and "normal" (or current) electricity

The gold leaf electroscope

Electricity Quiz



Motors / Generators




Electricity and magnetism are two faces of the same thing: electromagnetism.

This was first observed by Faraday, in England, in the nineteenth century.

In his experiments he found that a moving magnet can induce an electric current in a nearby wire. This phenomenon is called electromagnetic induction (the term induction means that there is no contact between magnet and wire).

On the other hand, electric currents produce magnetic fields.

This discovery was a great unification in physics (read text on the left).

Electromagnetic induction is extremely important in engineering, as it is the basis of transformers, electric motors and generators, among other technologically important devices.

Maxwell, also in England, extended the electromagnetic theory by making a remarkable calculation: using two constants, that are measured in experiments involving electromagnetism, he calculated the speed of light!

Maxwell found that light is an electromagnetic wave. It consists of oscillating magnetic and electric fields, which propagates even in vacuum.

Light is only a small fraction of what is known as the electromagnetic spectrum, that ranges from radio-waves (low frequency), to micro-waves, infra-red, light, UV, x-rays and gamma rays (high frequency).