What Is an Electromagnet?
Electromagnets are a useful tool, yet the general image of them in the public imagination is the things used to pick up scrap cars at the junkyard and drop them into the compactor. In reality, it is hard to imagine a person finishing a day in modern society without coming into contact with at least one electromagnet, and more than likely several of them. Electromagnets and what they do are an important, fundamental modern technology, so much of what we take for granted would be difficult or impossible without them.
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Identification
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An electromagnet is a device that uses the flow of electric current to produce a magnetic field. This is not the same thing as an object that has been magnetized. An electromagnet loses its magnetic field when the current is switched off; a magnetized object remains magnetic.
Features
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Electricity passing through a wire is sufficient to create a magnetic field (although in household applications, this field is very weak). The simplest electromagnet design involves wrapping a wire around a tube to create a coil and then passing current through it. The field can be dramatically magnified by placing a ferromagnetic substance, such as iron, inside the coil tube.
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Benefits
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The principle benefit of an electromagnet over a permanent magnet is that the current can be raised, lowered or simply switched off, allowing the magnetic field to be manipulated in various ways. They are also generally easier to manufacture for applied uses than permanent magnets.
Function
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Electromagnets are a widely used device. They are found in generators, industrial lifting magnets, loudspeakers, magnetic tape (as in VHS and audio cassettes), motors, particle accelerators and telephone relays.
History
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The first electromagnet was built by British scientist William Sturgeon in 1823. He simply wrapped a wire around a varnished iron horseshoe and hooked it up to a battery. The design was relatively weak due to poor insulation, but nonetheless a device weighing little more than a mere half dozen ounces could lift 9 lb. magnetically.
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