While potentiometers and rheostats are built the same way, the simple fact is that they are two very different things. Most electricians use rheostats to alter a current, and potentiometers to produce varying voltages. They both use variable resistors to perform these specific functions.
The thing is, potentiometers can work as rheostats, but not all rheostats can function as potentiometers. Rheostats are also much heavier, as they are commonly used in high power situations. Spectra Symbols explains the difference between these two variable resistors further in the following discussion:
A rheostat is a two-terminal variable resistor used to control power to a load, without interrupting current flow. It functions as an adjustable resistor between the source of electricity and a device that uses adjustable current. Rheostats are commonly used to set lighting levels without needing to change the lights.
Rheostats use the principles of Ohm’s Law, which states that the current is inversely proportional to resistance for a given voltage. This enables an object, like a dimmer switch, to produce a lower output level. It is important to remember that rheostats are not polarized to they can work in reverse.
A potentiometer or a slider is a three-terminal variable resistor that enables a voltage signal to be tapped off from the slider. It establishes the levels of output in many electrical devices. Potentiometers have less power and are commonly used to control audio and television brightness. They also function as position transducers in joysticks and other devices that use the same mechanism.
There are different types of potentiometers available today. There are manually adjustable potentiometers, which can be divided in rotary or linear movement types. There are also electronically controlled resistors, called digital potentiometers.
Both potentiometers and rheostats are resistors used in adjusting elements for signals in electronic and mechanical devices. A potentiometer, however, is low power and commonly used for television and audio components. It is important to know the differences in their power capacity to determine which resistor is most appropriate for your project.