Which statement describes a rheostat?

• A. Fixed resistor with two terminals
• B. An adjustable resistor that has 2 terminals
• C. A device that stores energy
• D. A device that measures temperature

Answer: (B)

A rheostat is a device that changes current by varying resistance, and it is used as a two-terminal adjustable resistor. The common construction is a resistive element with a movable contact (wiper); when you connect two terminals, you can slide the contact to change how much of the element is in the circuit, thus adjusting the resistance. This distinguishes it from energy-storing components like a capacitor or inductor, and from temperature sensors. A potentiometer is similar in principle but normally has three terminals; when used as a rheostat it is used with two terminals, but the standard description of a rheostat is specifically a two-terminal adjustable resistor. So the statement that best describes a rheostat is an adjustable resistor that has 2 terminals.