The Physics of an Electric Motor

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The Physics of an Electric Motor

An electric motor is a device used to convert electric energy into rotational kinetic energy. There are two different types of electric motors, and each has there own use. The different types are direct current and alternating current motors. Each of these motors will be analyzed in the following.

To understand how this motor works, we must understand the relationship between electricity, and magnetism or simply put electromagnetism. Direct electric current in a simple description: There are two requirements for current flow. The first is a source of electrical potential energy or EMF (electro motive force,). The second is a conductor that provides a complete loop to carry the current. The reason a conductor will conduct is found on the atomic level. A conductive atom’s valance shell is not completely full electrons will flow from atom to atom because of this. When these electrons move from one atom to another that is electrical current (a brief description that is).

A magnet can be made from different materials, but loadstone is the natural form. The most important part of magnetism to make electric motors work is: A magnet has two different ends, or poles a north and a south pole. These poles behave like electric charges, like poles repel and unlike poles attract although magnets have no affect on still charges. The relationship between electricity and magnetism is that each phenomenon is that each generates a field. Electric fields can be pictured by thinking in terms of gravitational forces. Where, any two objects have a gravitational force one another. Any two electric charges have a force between them (either repelling, or attracting depending on polarity). These electric fiel...

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increases in the opposite or negative direction until it attains maximum negative value at 270 degrees, and finally decreases to zero value again at 360 degrees. It follows, then, that the induced emf can be completely described by the relation.

v+Vmaxsin(angular position of coil)”(cookeadamsdellmoore pg 509)

This hopefully adds some insight into the use of electric motors, and the principals of them that make these motors work. Such as electromagnetism, binary switches for DC motors, and the selection of a running frequency of a motor through the use of an oscillator.


Physics a world view forth edition: Larry D. Kirkpatrick, Gerald F. Wheeler; copyright 1992

Basic Mathematics for Electronics seventh edition: Nelson M. Cooke, Herbert F.R Adams, Peter B. Dell, T. Adair Moore; Copyright 1960
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