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 in the hole, denoting the center of the coil. The magnetic field disappears when the current is turned off. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet.
invented by Carl Josef Bayer
The Bayer process is the principal industrial means of refining bauxite to…
invented by Charles Martin Hall Paul Heroult
The Hall–Héroult process is the major industrial process for smelting…
invented by Isaac Charles Johnson
Portland cement is the most common type of cement in general use around the…
invented by John Walker
A match is a tool for starting a fire. Typically, matches are made of small…
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