04-12-2012, 02:15 PM
Magnetic Effects Of Electric current
Magnetic effcts of current.pptx (Size: 4.43 MB / Downloads: 34)
History #1
Term comes from the ancient Greek city of Magnesia, at which many natural magnets were found. We now refer to these natural magnets as lodestones (also spelled loadstone; lode means to lead or to attract) which contain magnetite, a natural magnetic material Fe3O4.
Pliny the Elder (23-79 AD Roman) wrote of a hill near the river Indus that was made entirely of a stone that attracted iron.
History #2
Chinese as early as 121 AD knew that an iron rod which had been brought near one of these natural magnets would acquire and retain the magnetic property…and that such a rod when suspended from a string would align itself in a north-south direction.
Use of magnets to aid in navigation can be traced back to at least the eleventh century.
Finally, the Science
Not until 1819 was a connection between electrical and magnetic phenomena shown. Danish scientist Hans Christian Oersted observed that a compass needle in the vicinity of a wire carrying electrical current was deflected!
In 1831, Michael Faraday discovered that a momentary current existed in a circuit when the current in a nearby circuit was started or stopped
Shortly thereafter, he discovered that motion of a magnet toward or away from a circuit could produce the same effect.
The Connection is Made
SUMMARY:
Oersted, the scientist showed that magnetic effects could be produced by moving electrical charges; Faraday and Henry showed that electric currents could be produced by moving magnets
Magnetic field around a magnet
Characteristics of magnetic field lines
1. Magnetic field lines emanate from the North Pole and terminate at the South Pole of a magnet.
2. The degree of closeness of magnetic field lines represents the relative strength of the magnet.
3. No two field lines can intersect each other