How does a rheostat work?

A rheostat functions as a variable resistor and is primarily used to control current in an electrical circuit by adjusting resistance. When the resistance of the rheostat is increased, the current flowing through the circuit decreases, and conversely, when the resistance is decreased, the current increases. This adjustability allows for fine control of electrical devices, such as dimming lights or adjusting the speed of a motor, making rheostats valuable in various applications.

The reason other options do not accurately describe a rheostat lies in their definitions: it does not increase voltage (rather, it directly influences current flow through resistance); it does not act as a fuse, which is designed to break the circuit when excessive current flows; and it does not generate a constant current flow, as that would imply a fixed resistance, while a rheostat is intentionally variable.