Multiturn potentiometers are also operated by rotating a shaft, but by several turns rather than less than a full turn.Some multiturn potentiometers have a linear resistive element with a sliding contact moved by a lead screw; others have a helical resistive element and a wiper that turns through 10, 20, or more complete revolutions, moving along the helix as it rotates.The only point of ingress for contamination is the narrow space between the shaft and the housing it rotates in.Another type is the linear slider potentiometer, which has a wiper which slides along a linear element instead of rotating.Multiple resistance elements can be ganged together with their sliding contacts on the same shaft, for example, in stereo audio amplifiers for volume control.
In principle any relationship is possible, but for most purposes linear or logarithmic (aka "audio taper") potentiometers are sufficient.
Potentiometers are rarely used to directly control significant power (more than a watt), since the power dissipated in the potentiometer would be comparable to the power in the controlled load.
Drawing of potentiometer with case cut away, showing parts: (A) shaft, (B) stationary carbon composition resistance element, (C) phosphor bronze wiper, (D) shaft attached to wiper, (E, G) terminals connected to ends of resistance element, (F) terminal connected to wiper.
When a percentage is referenced with a non-linear taper, it relates to the resistance value at the midpoint of the shaft rotation.
A 10% log taper would therefore measure 10% of the total resistance at the midpoint of the rotation; i.e.