What is a Rheostat?

A rheostat is a variable resistor.

As a variable resistor, it serves to vary the amount of voltage or current in a circuit.

Just like potentiometers, rheostats can be used to vary AC or DC signals.

They differ from potentiometers in the fact that they only have two leads of which potentiometers have 3. However, the two still achieve the same function. While a potentiometer uses a third terminal to serve as the adjustable part, the rheostat uses a slider to vary resistance. If the slider isn't moved, the rheostat functions as a fixed resistor.

A rheostat is connected in a circuit by having the two leads connected in series with the load.