Which variable resistor has three contacts and is used to adjust the output voltage?

Which variable resistor has three contacts and is used to adjust the output voltage?

• A. Rheostat
• B. Potentiometer
• C. Preset variable resistor
• D. Capacitor

Answer: (B)

A potentiometer is a three-terminal device that functions as a voltage divider, giving an adjustable output voltage. The resistive element has two fixed ends and a movable contact, the wiper, that slides along the track. By turning the knob, you change the position of the wiper, which changes the ratio of resistance from the top end to the wiper and from the wiper to the bottom end. The output is taken from the wiper, so the voltage you get at the output varies as you move it. A rheostat uses only two terminals and is meant to vary resistance to control current, not provide a tunable output voltage. A preset variable resistor (trim pot) also has three terminals but is typically used for calibration and not as a user-adjustable voltage output in a circuit. A capacitor is not a resistor at all. So the device designed to adjust the output voltage with three contacts is the potentiometer.

A potentiometer is a three-terminal device that functions as a voltage divider, giving an adjustable output voltage. The resistive element has two fixed ends and a movable contact, the wiper, that slides along the track. By turning the knob, you change the position of the wiper, which changes the ratio of resistance from the top end to the wiper and from the wiper to the bottom end. The output is taken from the wiper, so the voltage you get at the output varies as you move it.

A rheostat uses only two terminals and is meant to vary resistance to control current, not provide a tunable output voltage. A preset variable resistor (trim pot) also has three terminals but is typically used for calibration and not as a user-adjustable voltage output in a circuit. A capacitor is not a resistor at all.

So the device designed to adjust the output voltage with three contacts is the potentiometer.