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Run on seatwork (1)


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Run on seatwork (1)

  1. 1. Electromagnet Electromagnet is a device that has magnetic properties only when an electric current isapplied to it, the electromagnet is an essential part of electric generators and motors it is alsoused in many other devices, including electric bells, tape recorders, circuit breakers, andscientific instruments called particle accelerators. Large electromagnets, attached to cranes, areused to lift huge loads of metal. The simplest electromagnet is a coil of insulated wire the magnetism it produces isweak. However, for practical purposes, the wire is wound around an iron core, greatlyincreasing the magnetic strength. In 1820, Hans Christian Oersted, a Danish physicist, discovered that an electric currenthas magnetic properties William Sturgeon, an English physicist who used the principle ofOersted, made the first electromagnet in 1823, Joseph Henry, a United States physicist, greatlyimproved Sturgeons design in the late 1820s.Special Types of Electromagnets A Relay is an electromagnet used as a switch to permit one electric circuit to control theoperation of one or more additional circuits, the switch contacts are moved by theelectromagnet rather than by hand. Relays are used in many control devices, including furnacecontrols and automobile electrical circuits. A Solenoid can be used as a relay or to control mechanical equipment it consists of a coilwound on a nonmagnetic cylinder, inside of which is an iron plunger free to move. Whencurrent is applied, the plunger is attracted into the coil. With this action, the plunger eithercloses an electric switch or pushes against a lever.Source: accessed 02 December 2012.