The Spirit of Electricity

The Spirit of Electricity

Introduction

Electricity is a form of energy, a phenomenon that is a result of the existence of electrical charge. The understanding of electricity has led to the invention of motors, generators, telephones, radio and television, X-ray devices, computers and nuclear energy systems. Electricity is a necessity to modern civilization.

From Day One

Legend has it that the word magnet comes from Magnesia a type of rock found in Asia Minor. These rocks were natural and formed from an iron ore now known as Magnetite. The rocks were believed to have great powers, which ranged from curing many ailments to attracting lovers.

Around 376 B.C. Haung Ti a Chinese general had his attention drawn to the fact that a piece of Magnetite, when suspended from a thread, would align itself with the direction of the Earth's North and South. He quickly employed this knowledge with his soldiers to help them find their way over the long distances they travelled. The compass was born.

In the seventh century B.C. Thales a Greek philosopher and mathematician noticed that by rubbing the stone amber on cloth it would attract light objects and hence he believed that the amber became magnetic. Even so he was troubled by the fact that his rubbed amber could not pick up metals and yet Magnetite would attract iron without having to be rubbed.

Unfortunately as far as we know he did not attempt to gain an

answer to this problem. We now realise that Thales had not been

able to separate the difference between Static electricity on the

Amber and Magnetism in the Magnetite.

By the year 1600, the compass was in common use but it was William Gilbert the Physician to Queen Elizabeth l who returned to Thales's perplexing problem of amber acting like a magnet. He derived the word 'Electrica' to refer to substances that acted like amber. The word 'Electrica' comes from the Latin for amber, 'Electrum', which in turn was derived from the Greek word for amber, Electra'.

From this point many studies of this new force began in 1660 Otto Von Guericke built the first static electricity generator: a glass ball turned by hand which rubbed against a cloth, would create sparks of static electricity. 73 years later the Frenchman Charles Dufey discovered that statically charged materials would react like magnets by either attracting or repelling each other. He deduced that there were two types of electricity. This claim of thought was continued by Benjamin Franklin and he referred to the two electricity's as positive and negative.

Lightning

In 1747, Benjamin Franklin in America and William Watson (1715-87) in England independently reached the same conclusion: all materials posses a single kind of electrical "fluid" that can penetrate mater freely but that can be neither created or destroyed. The action of rubbing merely transfers the fluid from one body to another, electrifying both.

Benjamin Franklin is best known for flying a kite in a lightning storm in 1752. In fact there was no lightning when he flew the kite. This was just as well because at about the same time a Russian Scientist was killed while holding a metal rod up during a storm. Even without the lightning in Franklin's storm he was still able to generate an electrical charge from his kite and therefore proved that lightning was indeed electricity built by storms.

Electric Potential

In the 18th-century Italian scientist Luigi Galvani started a chain of events that culminated in the development of the concept of voltage and the invention of the battery. In 1780 one of Galvani's assistants noticed that a dissected frog leg twitched when he touched its nerve with a scalpel. Another assistant thought that he had seen a spark from a nearby charged electric generator at the same time. Galvani reasoned that the electricity was the cause of muscle contractions. he mistakenly thought, however, that the cause of muscle contractions. He mistakenly thought, however, that the effect was due to the transfer of a special fluid, or "animal electricity," rather than to conventional electricity.

Experiments such as this, in which the legs of a frog or bird were stimulated by contact with different types of metals, led Luigi Galvani in 171 to propose his theory that animal tissues generate electricity.

The Battery

In experimenting with what he called atmospheric electricity, Galvani found that a frog muscle would twitch when hung by a brass hook on an iron lattice. Another Italian, Alessandro Volta, a professor at the University of Pavia, affirmed that the brass and iron, separated by the moist tissue of the frog, were generating electricity and that the frog's leg was simply a detector. In 1800, Volta succeeded in amplifying the effect by stacking plates made of copper, zinc and moistened pasteboard respectively and in so doing he invented the battery.

A battery separates electrical charge by chemical means. If the charge is removed in some way, the battery separates more charge, thus transforming chemical energy into electrical energy. A battery can affect charges, for instance, by forcing them through the filament of a light bulb. Its ability to do work by electrical means is measured by the volt, named for Volta. A volt is equal to 1 joule of work or energy (1 joule = 2.78/10,000,000 kilowatt-hours) for each coulomb of charge. The electrical ability of battery to do work is called the electromotive force, or emf.

Alessandro Volta (1745-1827) invented the first electric battery known as the voltaic pile, in 1800. Voltaic piles consisted of a stack of alternating discs of zinc and copper or silver separated by felt soaked in brine. They provided, for the first time, a simple source of stored electrical energy that did not rely on mechanical means.

Electromagnetism

The advent of the battery meant that more experiments could be carried out with a reasonably controllable and sustained flow of electricity. During one experiment in 1820, Hans Christian Oersted noticed that a current of electricity would cause a deflection on a compass needle. From this observation, Oersted deduced that there was a relationship between electricity and magnetism, as Thales had naively thought, and introduced the world to electromagnetism.

Oersted's