What device is a variable resistor used to provide a variable voltage?

What device is a variable resistor used to provide a variable voltage?

• A. Rheostat
• B. Potentiometer
• C. Fixed Resistor
• D. Thermistor

Answer: (B)

A potentiometer provides a variable voltage because it’s a three-terminal device that works as a voltage divider. Connect the two ends across a fixed supply and use the wiper as the output; moving the knob changes the ratio of resistance on either side, so the output voltage varies from near zero up to the full supply. A rheostat is a two-terminal device used to vary current by changing resistance in series, not to supply a variable voltage to a separate circuit. A fixed resistor doesn’t change, and a thermistor changes resistance with temperature rather than by user adjustment.

A potentiometer provides a variable voltage because it’s a three-terminal device that works as a voltage divider. Connect the two ends across a fixed supply and use the wiper as the output; moving the knob changes the ratio of resistance on either side, so the output voltage varies from near zero up to the full supply. A rheostat is a two-terminal device used to vary current by changing resistance in series, not to supply a variable voltage to a separate circuit. A fixed resistor doesn’t change, and a thermistor changes resistance with temperature rather than by user adjustment.