A resolver is best described as which of the following?

• A. A device to measure humidity
• B. A device for converting AC to DC
• C. A revolving transformer used to measure the degrees of rotation in a motor
• D. A temperature sensor

Answer: (C)

Angular position sensing is the key idea. A resolver is a rotating transformer that turns shaft position into electrical signals used for feedback in control systems. When the shaft rotates, the resolver’s winding arrangement produces two output voltages that vary with angle—essentially encoding the rotation as sine and cosine signals. These signals let the control system determine the exact degrees of rotation, providing precise position feedback for motors and servo systems. The other options describe sensors or devices for unrelated measurements—humidity, or temperature—or a device that converts AC to DC. So the revolving transformer that outputs angle-dependent signals matches what a resolver does.