Potentiometer

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schematic symbol for a potentiometer

A potentiometer is a variable resistor.

Usually, this is a three-terminal resistor where the center connection is manipulable. If two terminals are used (middle and end), it acts as a variable resistor. If all three are used, it acts as a variable voltage divider. A common application for such devices is as a volume control in audio equipment.

A typical single turn potentiometer

Typically, a potentiometer is constructed as a flat circular graphite contact to generate resistance, with a wiper on an axle connected to the center terminal. This wiper typically travels just under one revolution around the contact. However, multiturn potentiometers also exist, where the contact may be helical and the wiper may move 10, 20, or more turns.

Also, the potentiometer may be linear, to provide a slider control instead of a dial control.

A rheostat is essentially a potentiometer, but is usually much larger, designed to handle much higher voltage and current. Typically these are constructed as a resistive wire wrapped around a toroidal core with the wiper moving over the upper surface of the toroid, sliding from one turn of the wire to the next.