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rheostat




A variable resistor used to control current drawn by an electric motor, to dim lighting, etc. It may consist of a resistive wire, wound in a helix, with a sliding contact varying the effective length, or a series of fixed resistors connected between a row of button contacts. Or, for heavy loads, electrodes dipped in solutions can be used, the resistance being controlled by the immersion depth and separation of the electrodes.


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   • ELECTRICITY AND MAGNETISM