The command of electricity
Imagine a world without electricity ... no phones, no computers, no lights, no fridges.
Without our command of electricity, the world would be a very different place.
This control, however, has only come about in the last 150 years or so.
Large quantities of electricity can't be stored electricity for mass public supply has to be generated on demand. Professor James' article explores the story of electricity and some of the early inventions that made public supply achievable.
Portrait of Michael Faraday
, courtesy of the Royal Institution. In the background is the 50 inch diameter plate machine made for Napoleon. It is designed to generate electrostatic electricity using the principle of rubbing. The plate is made of glass. The machine ended up at the Royal Institution, where Faraday used it in his experiments.
The command of electricity
by Frank A.J.L. James
, Professor of the History of Science, The Royal Institution
"Electricity reveals new worlds. They are pigmy worlds, you might think; but who knows that one day giants too may amuse themselves with them".
Beccaria to Boscovich, 22 April 1768
The effects of electricity have been known about since antiquity. Indeed, the word 'electricity' comes from the Greek word for the fossil resin called amber ηλετρου. The Greeks had observed something special about the material.
They had noticed that when amber is rubbed it produces a repulsive force. What's happening is that rubbing amber gives it a coating of negatively charged electrons. When approached by a similarly charged body, the amber pushes the second object away.
Also known about in the ancient world were the phenomena of lightning and the (electric) shock produced by the Mediterranean fish called the torpedo.
It is doubtful whether anybody at that time realised that all these phenomena were connected by electricity
. Indeed, it was not until the 18th century that it was found that both lightning and the torpedo's shock were electrical.
The American natural philosopher and statesman, Benjamin Franklin, showed directly, by having a kite flown during a thunder storm, that lightning was electrical in nature. This led him to suggest the idea of a metal conductor placed on top of buildings and connected to the earth, to protect them from the effects of lightning strikes, which were more of a problem in North America than in Europe.
As far as electric fish were concerned, a number of British savants studied how the torpedo produced its shock. By identifying the electrical organs of the fish they were able to demonstrate the intimate link between electricity and life.
However, it was the sort of electricity produced by amber that was most studied in the 18th century. New methods of creating ever-more powerful machines to make such electricity were developed, based on the principle of rubbing.
It was found that glass was the easiest material to use. The first type of machine consisted of a cylinder of glass that was rotated to rub against a cloth, and the charge created was taken off the glass. A method of storing such electricity was invented by Pieter van Musschenbroek (1692-1761) of Leyden. In his method, the electric fluid as it was then thought to be was stored in what became known a Leyden jar, a series of which could be arranged in batteries to store large quantities of charge.
Later in the 18th century, the cylinder machine was replaced by the plate machine in which a circular plate of glass was rotated against a cloth.
Some quite large machines of this sort were made, including one 50 inches in diameter for the Emperor Napoleon that eventually found its way to the laboratory of the Royal Institution in London. It was used by Michael Faraday
, and is indeed depicted in one of his portraits (shown at left). Unfortunately, it no longer exists.
The plate machine was the forerunner of the Wimshurst machine invented in the late 19th century but now displaced for most purposes by the Van de Graaff generator
. Although some generators can produce millions of volts, they work on exactly the same principle of rubbing that the Greeks observed.
In the 18th century, such electricity had no practical use. However, because of the spectacular effects it created, such as large sparks and loud crackles, electrical demonstrations had considerable amusement value. Another example is raising peoples' hair by discharging a charge-making machine into them. Itinerant lecturers toured the country giving demonstrations of the effects of electricity.
Franklin's discovery of the electrical nature of lightning was put to good use in the form of the thunder house. A small model of a house was made and when the electricity from a machine or Leyden jar was discharged into it, producing a lightning-like spark, the house fell apart.
Until the end of the 18th century, the term electricity
only referred to electricity produced by rubbing, since this was the only form that could be controlled and studied. In Italy the 1790s, Alessandro Volta (1745-1827)
found that if pieces of different metals were piled on top of each other separated by cardboard soaked in an acid, an electric current was produced by chemical means. He had discovered voltaic electricity and invented the voltaic pile or battery
, as it became known.
With this discovery, electricity produced by rubbing started to be referred to as common or frictional electricity, and eventually as electro-statics, since it was realised that voltaic electricity is dynamic in that it moves through a wire, while common electricity is stationary on a surface until it's discharged.
The electric battery was the essential first step to using electricity in practical ways. This is because voltaic electricity has (comparatively) high power
and low tension
, while common electricity had high tension but very low power. This is why it's possible for a person to have a spark discharged into them but not advisable to touch a live mains wire.
In the ensuing decades, this new source of electricity was studied extensively. In 1931, Michael Faraday
was able to make it by moving a magnet in a coil he invented the electric generator
. You can read about this invention and how he did it, see electrical generator >
By the end of the 1830s, electricity had found its first practical use with the invention of the electric telegraph by Charles Wheatstone and William Cooke. In the 1860s, the Atlantic telegraph cable was laid, reducing the speed of communication between the Old and New Worlds from weeks to minutes.
Faraday's method of generating electricity magnetically was the key to allowing large scale practical use of electricity for power. The problem is that large quantities of electricity cannot be stored.
This means that the quantity of electricity generated at any given time has to balance demand, which is why the distribution system is crucial to the use of electricity. The simple act of flicking a light switch engages a massive national system of generation and supply.