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An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated along the center of the coil. The magnetic field disappears when the current is turned off.
Permanent magnets can be described without reference to electricity or electromagnetism. Circuit theory deals with electrical networks where the fields are largely confined around current carrying conductors. In such circuits, even Maxwell's equations can be dispensed with and simpler formulations used.
A theory of electromagnetism, known as classical electromagnetism, was developed by several physicists during the period between 1820 and 1873, when James Clerk Maxwell's treatise was published, which unified previous developments into a single theory, proposing that light was an electromagnetic wave propagating in the luminiferous ether. [26]
There is a 1–10 cm (0.39-3.93 inch) air gap between that eliminates friction, allowing for speeds up to 500 km/h (310 mph). [7] An alternating electric current is supplied to the coils, which creates a change in polarity of the magnetic field. [8] This pulls the train forward from the front, and thrusts the train forward from the back. [9]
A deflection yoke (copper coils and white plastic former) around the rear neck of a cathode ray tube television View inside the yoke, with the tube removed. Television sets employing cathode ray tubes use a magnetic lens in the form of a deflection yoke to enable an electron beam to scan the image by deflecting it vertically and horizontally.
The first usage of the word electricity is ascribed to Sir Thomas Browne in his 1646 work, Pseudodoxia Epidemica. The first appearance of the term electromagnetism was in Magnes, [35] by the Jesuit luminary Athanasius Kircher, in 1641, which carries the provocative chapter-heading: "Elektro-magnetismos i.e.
Ace trivia night with these cool and random fun facts for adults and kids. This list of interesting facts is the perfect way to learn something new about life. 105 Fun Facts About Science, History ...
On June 25, 1876, Bell's experimental telephone, using a different design, was demonstrated at the Centennial Exhibition in Philadelphia, where Henry was one of the judges for electrical exhibits. On 13 January 1877, Bell demonstrated his instruments to Henry at the Smithsonian Institution and Henry invited Bell to demonstrate them again that ...