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Unformatted text preview: A Brief Outline of the History of Electromagnetism Richard Alan Peters II April 5, 2000 The primary sources for this outline were From Falling Bodies to Radio Waves , Emilio Segr` e, Freeman, New York, 1984, A History of Electricity and Mag- netism , Herbert W. Meyer, MIT Press, Cambridge, MA, 1971, Physics , 3rd ed. David Halliday and Robert Resnick, Wiley, New York, 1978, and Encyclopedia Britanica . 1. Ancient Electrical, magnetic, and optical effects have been known since antiquity. – the ability of some materials, notably amber, when rubbed to attract bits of cloth or paper and the lodestone or natural magnet. 2. Early Systematic investigation did not occur until the middle ages. Mag- netic phenomena were first explored. The magnetic compass was known in 12th century England and not considered a novelty. In the 13th cen- tury, Petrus Peregrinus de Maricourt (France) found that when a a magnetized needle was placed on a spherical magnet it would align itself longitudinally. Tracing the lines, he showed that they intersected in two points on opposite sides of the sphere. He called these, “magnetic poles”. He also showed that the orientation of a magnetic needle near the sphere depended on its proximity to a pole. 3. William Gilbert , (1540-1603). Physician to QEI, time of Shakespeare, the Spanish Armada. Published De Magnete in 1600. He confirmed Pere- grinus’s result and speculated that the Earth is giant magnet. Showed that friction caused the attractive phenomenon to appear in many mate- rials. He called the property “electric” from the Latin word, electrum , for amber. Gilbert attributed the electrification of a body by friction to the removal of a fluid or “humor” which then left an “effluvium” or atmosphere, around the body. Replace humor with charge and effluvium with electric field to see that he was on the right track. 4. Otto Von Guericke , (1602-1688), Burgermeister of Magdeburg, Ger- many; he was trained as an engineer. Invented the vacuum pump – as- tounded people with a demonstration that 2 opposing teams of 8 horses 1 each could not separate two evacuated hemispheres. He was interested in the behavior of phenomena in a vacuum; tried to understand forces, such as gravity, that would act at a distance. He built the first electrostatic generator (based on friction). 5. Stephen Gray , (1666-1736). the son of a dyer from Canterbury, England. He discovered that the charge on an electrified body could be extended from that body. He found the effect worked using some materials and didn’t work with others. He was able to distinguish conductors from insulators . . . . But for static charges. Currents were as yet unknown....
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- Spring '09
- Magnetism, Magnetic Field, Electric charge