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Resistances+Rheostats

Electrical resistance on Fotopedia

The electrical resistance of an object is a measure of its opposition to the passage of a steady electrical current. An object of uniform cross section will have a resistance proportional to its length and inversely proportional to its cross-sectional area, and proportional to the resistivity of the material. Discovered by Georg Ohm in the late 1820s, electrical resistance shares some conceptual parallels with the mechanical notion of friction. The resistance of a resistive object determines the amount of current through the object for a given potential difference across the object, in accordance with Ohm's law. (Wikipedia)