What is the main characteristic of a rheostat switch?

A rheostat switch is primarily characterized by its ability to vary resistance within an electrical circuit. Unlike a fixed resistor, which has a set resistance value, a rheostat allows users to adjust the resistance level by turning a knob. This adjustability enables fine-tuning of the current in the circuit, making it useful in applications like dimming lights or controlling motor speeds.

The key aspect of a rheostat is that it changes the resistance in response to the position of the knob, providing flexibility in controlling the voltage and current in a circuit. This characteristic is fundamental to its design and function, distinguishing it from other types of switches that might only provide a binary on/off function or operate at fixed resistance values.