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Magnet wire is a thinly insulated wire made of either purified and fully-annealed copper or aluminum. When coiled and energized by an electrical power source the wire will produce an electromagnetic field. Nearly all electricity needs to be routed through an electromagnetic field to convert from one form of energy to another. Magnet wire can be used to transform energy between three different ways: from one form of electrical energy to another, mechanical energy to electrical energy, and electrical energy to mechanical energy.
Apparatuses that transfer power from one voltage and amperage to another voltage and amperage use magnet wire to accomplish this. Examples are transformers, electrical controls, and power generation. The ignition coil of an automobile transforms 12 volts of a car battery into thousands of volts necessary to start the car.
Magnet wire is involved in the transfer of electrical energy into mechanical energy. Examples are machinery and electric motors. Advances in the development and manufacture of magnet wire contributed to the mass construction of electric motors, greatly impacting the growth of manufacturing in the twentieth century.
A third application is converting mechanical energy to electrical energy. Generators are machines that use electromagnetic coils to produce electric power. A coil of wire rotates between two magnetic poles, producing an electric current that increases and decreases as the coil moves toward and away from each magnetic pole, changing direction each time it approaches a pole. This type of current is alternating current, or AC.
Most magnet wire is made of copper, a highly conductive material that can be manufactured in very fine gauges ranging from a few microns to several centimeters. Sometimes aluminum is used in large transformers or motors. Since aluminum is not nearly as conductive as copper, it’s typically square or rectangular, since it needs more diameter to approach a similar resistance to copper.
Modern insulating material varies depending on the temperature in which it will be used. One to three layers of polymer is suitable for most applications, even when used in high heat situations. Glass is used for wire used in electrical generators, motors, and mining equipment. Paper coatings are used for oil-filled and utility transformers.
Initially, magnet wire was insulated with cloth. Inventor George Jacobs, founder of Dudlo Manufacturing, developed the enamel insulation process that made production of copper wire in fine gauges possible. During World War II, magnet wire production increased to meet the demand for transformers, telephone wire, x-ray machines, military trucks, and B-24 bomber wiring harnesses.