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WPI Technical Theatre Handbook: Basic Theory
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Basic Theory

While it is well beyond the scope of this book to provide a full description of electrical engineering theory, there are several basic facts that should be understood by anyone working with electrical power. Note that this is an extremely simplified coverage of the topic, and that there are hundreds of books written about each of the topics discussed.

First, the most common voltages worked with are 110 and 220 volts, alternating current. Currents anywhere from a few milliamperes to hundreds of amps are used. Additionally, one, two and three phase power is used to run a variety of devices.

Alternating current is sinusoidal in nature, unlike the ``flat'' direct current provided by batteries. The current changes direction a given number of times a second, which, in the case of standard U.S. power , is 60 times a second.

Multiple phases of power are made up of several sinusoids, each ``aligned'' slightly differently with respect to time. That is to say, they are out of phase with respect to each other. This difference in phase can be used by efficient electrical motors, or ignored, as is the case much of the time when used for lighting or audio.

next up previous contents index
Next: Power Feeds Up: Power Previous: Introduction   Contents   Index
Steve Richardson 2000-07-06

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