cur rent

Science Dictionary
current  [%PREMIUM_LINK%]     (kûr'ənt)  Pronunciation Key 
  1. A flowing movement in a liquid, gas, plasma, or other form of matter, especially one that follows a recognizable course.

  2. A flow of positive electric charge. The strength of current flow in any medium is related to voltage differences in that medium, as well as the electrical properties of the medium, and is measured in amperes. Since electrons are stipulated to have a negative charge, current in an electrical circuit actually flows in the opposite direction of the movement of electrons. See also electromagnetism, Ohm's law. See Note at electric charge.


Our Living Language  : Electric current is the phenomenon most often experienced in the form of electricity. Any time an object with a net electric charge is in motion, such as an electron in a wire or a positively charged ion jetting into the atmosphere from a solar flare, there is an electric current; the total current moving through some cross-sectional area in a given direction is simply the amount of positive charge moving through that cross-section. Current is sometimes confused with electric potential or voltage, but a voltage difference between two points (such as the two terminals of a battery) means only that current can potentially flow between them; how much does in fact flow depends on the resistance of the material between the two points. Electrical signals transmitted through a wire generally propagate at nearly the speed of light, but the current in the wire actually moves very slowly: pushing electrons into one end of the wire is rather like pushing a marble into one end of a tube filled with marbles—a marble (or electron) gets pushed out the other end almost instantly, even though the marbles (or electrons) inside move only incrementally.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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