Make your own free website on Tripod.com

A Little History: Electricity and Magnetism

by M. M. Camaron

When my second daughter departed to set up home elsewhere, her bedroom became free space. It was, in fact, a loft conversion carried out some fifteen years ago and intended to provide me with an office. I decided that I must quickly convert this space for my own use before any other member of the family laid claim to it.

During the unbelievable upheaval that this apparently simple manoeuvre created, an old textbook - "Electricity and Magnetism" - came to light; it was first published in 1930 and written by a physics teacher called Nightingale. Work stopped for many hours as I read and became fascinated by this slim volume. It's funny to recall that whilst at school, virtually nothing but starvation would induce me to read such a work.

The text reminded me of the long and painfully slow progress that man had made in his attempts to gain an understanding of the nature of electricity. For centuries, all that man could do was to observe natural phenomena such as magnetism, static electricity, lightning and so on without any means of controlling or using them.

The mineral lodestone was discovered by the Greeks in the province of Magnesia, from which the word 'magnet' is derived, and they were amazed at its strange powers, such as attracting small pieces of iron. For centuries from that time on, nothing much seems to have happened (except innumerable wars), until in 1565, the Englishman William Gilbert, who was royal physician to both Elizabeth I and James I, discovered that magnets could be made by stroking pieces of iron with lodestone. From his experiments he concluded that the Earth acted as a giant magnet; his account of these, published in 1600 as "De Magnete", is often considered to be the first great scientific work written in England.

Now things really began to happen; I read that within another two hundred years it was discovered in Leyden, a town in Holland, that a glass vessel partly filled with water was found to be capable of holding a small electric charge. Thus was born the first capacitor - though they called it a Leyden Jar. The two plates of the capacitor were provided by coating the inner and outer surfaces of the glass with metal foil. Once again, folk were fascinated by this phenomenon, and one story relates how on one occasion a number of monks at either end of the chain, all were seen to rise simultaneously into the air!

About this time, various experiments began to explore the nature of lightning to see if this could be harnessed in any way. It seems that the old Hammer film showing Peter Cushing using leads from lightning conductors in an attempt to energise the Frankenstein monster has an element of truth about it. Benjamin Franklin, an American living in Philadelphia, thought it likely that lightning originated from electrically charged clouds, and in 1750 proposed to fix a kind of sentry box on the steeple of a new church, with a pointed metal rod passing out of the top of the box. Inside the box, a man on an insulated stool would be in contact with the rod. But the building of the church was delayed, so he decided instead to fly a kite up towards the thundercloud, and he found that the wet string did conduct enough electricity from the cloud to charge a large capacitor. These early electricians, as they were called, must have been men of considerable courage, because the devastating power of a lightning strike had been evident from the earliest times, and a number of them did in fact lose their lives during this period. But from these experiments the idea of fixing lightning conductors to buildings arose.

Around this time, Stephen Gray, sometimes referred to as the 'Father of Electrical Science' was experimenting in England with the generation and transfer of static electricity. At first he used long pieces of packthread suspended from iron nails driven into his ceiling beams; these did not conduct and he concluded that the electricity was escaping through the iron nails. So he suspended the string from silk thread, and found that the current would pass over a length of up to 100 yards to a live chicken he had attached to the other end. The chicken was seen to attract confetti and any other light items around it - what his wife said about the spectacle of a confetti clad chicken streaking across the kitchen in not recorded. It was Grey who first distinguished between conductors, such as the common metals, and insulators such as glass and silk. I've heard poor quality modern electrical installations described as 'wet string contracts'; perhaps this phrase dates back to the time of Gray and Franklin.

Having burnt out many diodes over the years through carelessness, I was heartened to read that other people has experienced similar disasters, and on a somewhat larger scale. The first submarine cable laid across the Atlantic was completed in 1858: a story of great persistence in the teeth of repeated failure. The pioneering engineers assumed that a high potential would be required to transmit signals along the 2000 miles of cable, and applied 2000 volts, which permanently damaged the cable insulation....nice one ! Incidentally, it took thirty hours to transmit the 150 word greeting exchanged between Queen Victoria and the American president, President ...... guess I wasn't any good at history either.

Another interesting paragraph described Wheatstone's early experiments with the telegraph, around 1837. One of the first systems was installed in 1841 between Paddington and Slough on the Great Western Railway. This invention must have seemed quite magical at the time, and the story goes that a Scotsman and his wife thought they would telegraph a pair of boots to their son, and after addressing them they hung them on the wires. To their delight, the boots had gone next day, and a message left on a piece of scrap paper read: "Boots safely received. Many thanks."

By this time, of course, Faraday was at the Royal Institution making his outstanding discoveries in the whole field of electricity, and the exponential curve of discovery was well under way.