A potentiometer is a / an?

• A. An electronic relay
• B. A P.E. switch
• C. A multicoil transformer
• D. A variable resistor

Answer: (D)

A potentiometer is a device that acts as a variable resistor. It contains a resistive track and a moving contact (the wiper) that slides along the track when you turn the knob. This motion changes the resistance between the wiper and either end, or creates two resistances in series that add up to the total track resistance. In many circuits it’s used as a voltage divider: applying a voltage across the two ends and taking the output from the wiper gives a controllable fraction of the input voltage. This adjustable resistance is why it’s used for things like volume or tuning controls. It’s not a relay (which is an electromechanical switch), not a pressure switch (which changes state based on pressure), and not a transformer (which transfers energy via magnetic coupling).