 - See also dielectric material. When two objects in each other's vicinity have different electrical charges, an electrostatic field exists between them. An electrostatic field also forms around any single object that is electrically charged with respect to its environment. An object is negatively charged (-) if it has an excess of electrons relative to itssurroundings. An object is positively charged (+) if it is deficient in electrons with respect to its surroundings. Electrostatic fields bear some similarity to magneticfields. Objects attract if their charges are of opposite polarity (+/-);objects repel if their charges are of the same polarity (+/+ or -/-). The lines of electrostatic flux in the vicinity of a pair of oppositely charged objects are similar to lines of magneticflux between and around a pair of opposite magnetic poles. Inother ways, electrostatic and magnetic fields differ. Electrostatic fields areblocked by metallic objects, while magnetic fields can pass through most (but not all) metals. Electrostatic fields arise from a potential difference or voltage gradient, and can exist when charge carriers, such as electrons, are stationary (hence the "static"in "electrostatic"). Magnetic fields arise from the movementof charge carriers, that is, from the flow of current. When charge carriers are accelerated (as opposed to movingat constant velocity), a fluctuating magnetic field is produced. This gives rise to a fluctuating electric field, which in turn produces another varying magnetic field. The result is a "leapfrog" effect, in which both fields canpropagate over vast distances through space. Such a synergistic field is known as an electromagnetic field, and is the phenomenon that makes wireless communications, broadcasting, and control systems possible.
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30 Oct 2007
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