When all three leads are used on a variable resistor, it is called a ?

• A. Potentiometer
• B. Rheostat
• C. Three-way stat
• D. Regulator

Answer: (A)

Using all three leads on a variable resistor forms a potentiometer. The outer two terminals are the ends of a resistive track, and the third lead is the wiper that slides along that track. When you connect the outer terminals to a source and a load and use the wiper as the output, you get a variable voltage divider—the output can be tuned by turning the knob. That three-terminal arrangement is what defines a potentiometer.

A rheostat, by contrast, uses only two leads (the wiper and one end) to vary current through a circuit, not a voltage divider. A term like three-way stat isn’t a standard device in this context, and a regulator is designed to hold a steady output, not to provide a variable voltage.