Electricity and Magnetism

The nature and effects of moving and stationary electric charges is called electricity. Charges that are stationary form static electricity. Electric charges in motion constitute electric current.

The study of the nature and the cause of the magnetic force field and how different substances are affected by them is called magnetism. Magnetic fields are produced by moving charge – on large scale (as with a current in a coil, forming an electromagnet), or on small scale of the moving charges in the atoms. It is generally assumed that the earth’s magnetism and that of the other planets, stars and galaxies have the same cause.

Science of electricity and magnetism developed quite separately for centuries, until 1820 in fact, when Hans Christian Oersted found a connection between them: an electric current in a wire can deflect a magnetic needle. Oersted made this discovery while he was preparing a lecture for his physics students.

This new science of electromagnetism was developed further by Michael Faraday. His collected laboratory notebooks do not contain a single equation. James Clerk Maxwell put Faradays ideas into the mathematical form, introduced many new ideas of his own and put electromagnetism into sound theoretical basis.

The development of classical electromagnetism did not end with Maxwell. Oliver Heaviside, H. A. Lorentz, Coulomb, Gauss, Heinrich Hertz and Marconi are the few to be mentioned. Albert Einstein based his theory of relativity on Maxwell’s equations.

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Applets

Wheatstone bridge

Wheatstone bridge(1)

Resistors in series

Resistors in parallel

Direct current electric motor

Electromagnetic oscillating circuit

Charged particle motion in a uniform magnetic field (2D)

Electromagnetic waves