The rotor in a shaded-pole motor consists of

a. coils energized by alternating current

b. a short-circuited loop of copper wire

c. a permanent magnet

d. an iron cylinder

The correct answer is b. a short-circuited loop of copper wire.

To find the answer, you can start by understanding the basic components of a shaded-pole motor. A shaded-pole motor is a type of single-phase induction motor commonly used in small appliances. It gets its name from the shading coils or shading rings that are present on the stator.

The main components of a shaded-pole motor are the stator and the rotor. The stator contains the main winding, which is energized by alternating current (AC), and the shading coils. The rotor, on the other hand, consists of a short-circuited loop of copper wire.

The purpose of the shading coils is to create a phase shift in the magnetic field of the stator, which in turn creates a rotating magnetic field. This rotating magnetic field interacts with the short-circuited loop of copper wire in the rotor, inducing a current in the rotor. This current generates another magnetic field that opposes the rotation of the motor. The interaction between these two magnetic fields creates a starting torque and causes the rotor to start rotating.

Therefore, the correct answer is b. a short-circuited loop of copper wire. It is this short-circuited loop that makes the shaded-pole motor a self-starting motor, where no external means of starting is required.