© 2008 Museum of Communication

This section covers the discoveries of the fundamental physical properties which allowed communication technologies to develop.

DID YOU KNOW: About 600 BC, the Greek philosopher Thales found that amber, when rubbed, had the property of attracting dry and light materials. As the Greek word for amber is ELECTRON, the property became known as ELECTRICITY

Electric current discharges between two electrical conductors (the metal nails). The voltage of the electric discharge must be large enough to jump across the non-conductive medium (the air or vacuum) between the conductors. If the voltage is too low the electricity will not flow. In everyday life electrical charges consist of an excess or a shortage of particles called electrons. Electrons are parts of atoms and have a negative electrical charge. In some materials, called conductors, some of the electrons are able to separate from their atoms and move relatively freely through the material. This flow of electrons is an electrical c urrent.

In the 18th Century, Allesandro Volta found that two dissimilar metals, separated by damp salt paper, produced a continuous current at low voltage. From this developed the Voltaic Cells, which led to Faraday's experiments with magnetic and electrostatic fields - and to the mathematics of James Clerk Maxwell.

Daniell, Leclanche and Poggendorf are all examples of the Voltaic Cells which provided the earliest reliable sources of electric current. The battery is still with us today, as these examples opposite show

Early electromagnetic offspring included the Cooke & Wheatstone telegraph, the Morse code and the telephone. In 1887 German physicist Heinrich Hertz, using Clerk Maxwell's theories, produced a 'spark transmitter' which generated, transmitted and received electromagnetic waves, proving the existence of radio waves.

Discs of amber or glass Rubbing Rods were rubbed vigorously with a piece of fur and the charge taken off successively by an Electrophorus - a piece of metal with an insulated handle. The electricity was then measured with a Gold Leaf Electroscope, stored in a Leyden Jar and the excess high voltage removed with Discharging Tongs.

In the late 18th century, this process was mechanised in the form of Friction Machines, of which Winter's Machine is an example, and later, by Influence Machines such as the Wimshurst Machine, which produced electricity in time separated, high voltage pulses.

The Induction Coil produced high voltages and generated sparks by breaking down the air insulation. Induction coils were the basis of early radio transmitters.