Potentiometer

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The term pot is used to refer to both variable resistors and potentiometers. The reason for this is that engineers use the same kind of component for two different jobs. A potentiometer uses three connections, a variable resistor just two.

Behind the volume control of your hi-fi lurks a pot. This consists of a horse-shoe shaped piece of resistive material (shown in orange in the diagram) with a moveable wiper contacting it (shown in blue).

The input signal is applied between the ends of the pot. The applied potential is then spread out along the horse-shoe shape. The output is taken between one end and the wiper. By rotating the wiper to touch the different places on the horse-shoe, we can 'tap-off' any fraction of the input voltage we want from zero up to the full size of the input. When we turn down the volume on the hi-fi we're moving the wiper towards the low-potential end. Turning up, moves the nearer the high potential (loud!) end.

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University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland.