Rheostat. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electricity for beginners
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A rheostat is a device designed to regulate the amount of current and voltage in an electrical circuit. Its main parts are a resistive element and a movable contact, with which you can smoothly or stepwise adjust the resistance of the part of the resistive element included in the circuit. To change the magnitude of the current or voltage, the rheostat is connected in series with the consumer of electricity.
Often the rheostat is made in the form of a wire coil of resistance, with the side surface of which a sliding contact comes into contact. When the contact is set so that only a few turns of the coil are included in the circuit, the resistance of the resistive element is minimal, there is practically no voltage drop across it, the current in the circuit is maximum and the light bulb shines with full light. When the sliding contact moves, an increasing number of turns of the coil are included in the circuit, the resistance of the resistive element increases, the voltage drop across it increases, the current in the circuit decreases, and the brightness of the light bulb decreases.
Rheostats are used, for example, to limit the starting current in electrical machines or as regulators and displacement sensors, when the resistance of the rheostat is proportional to the displacement (linear or angular).
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