When Electronics Was Young
The year 1831 was noteworthy for a number of reasons, none of them as yet connected with electronics per se:
1. Sir David Brewster (1781–1868) publishes his ‘Treatise on Optics’;
2. Independently, Michael Faraday (1791–1867) and Joseph Henry (1797–1878) discover that electricity can be induced by changes in a magnetic field—a discovery leading to the first electric generators;
3. Joseph Henry describes a practical electric motor;
4 Sir Charles Wheatstone (1802–1875) and William Fothergill (1799–1868) create the first printing telegraph, a machine with an arrow that points to letters of the alphabet;
5. The British Association for the Advancement of Science is established
6. Charles Darwin (1809–1882) begins his epic five-year voyage on the Beagle
7. An otherwise obscure von Jacobi discovered that the Earth may be used as a conductor.
Von Jacobi’s discovery is, of course, of great importance in electrical engineering. Yet, neither his name nor his discovery is mentioned in most modern reference books.
In that year, Faraday argued that, since Oersted had shown that a current could produce a magnetic field, a magnetic field should produce a current. He found this to be so, discovering the important property of electromagnetic induction (earlier discovered by Joseph Henry). In this work, Faraday introduced the idea of lines and fields of force, an idea which was to prove highly productive. It enabled him to devise primitive motors, a transformer, and a dynamo. Faraday also examined capacitors and the properties of dielectrics.
Electromagnetic induction, the conversion of magnetism into electricity, had been discovered in 1830 by Joseph Henry, but Henry had not published his findings. In 1832, he discovered self-induction and this time he published immediately. Consequently, the unit of self-induction is named after him. A coil has a self-inductance of one henry (H) if a change of current through it of one ampere per second produces a back emf of one volt across it.
Sir Charles Wheatstone who popularized but did not invent the bridge named after him (it was invented by S Christie) developed, together with Cooke, a device with separate control and switching sections. However, the first patent for such a relay (as it came to be known) was taken out by Edward Davy in 1838, although Cooke and Wheatstone’s patent was also accepted. Samuel Morse was granted a US patent in 1840 which is apparently similar to Davy’s patent.
Samuel Finley Breese Morse (1797–1872) made use of relays to develop the binary (on-off) telegraph system, which he put into practice in 1844 after he obtained a government grant to connect Baltimore and Washington DC. Electrical telecommunications had been borne.
Tags: communications, electronics, inventions, telegraph, year 1831