A potentiometer acts as a variable resistor or rheostat

Potentiometers—simple electromechanical devices that translate rotary or linear motion into a change in resistance—have been a cornerstone of measurement, control, and position systems for more than a century. In a standard potentiometer, one terminal is hooked up to a voltage source and the second to ground. A third terminal connects a sliding contact called a wiper that runs across a resistive track. As the wiper is moved across the resistive track, the voltage changes, corresponding to the new position. This voltage change can be used to control anything from volume or light intensity to the movement of complex mechanical systems. These three-terminal resistors with a sliding contact form an adjustable voltage divider, current divider, or other devices. When only two terminals are used (one side and the wiper), a potentiometer acts as a variable resistor or rheostat.