Electricity and Magnetism Practice Test

When you want a magnetic field produced by electric current, the essential element is a coil of wire—the solenoid. Passing current through many turns creates and concentrates a magnetic field inside the coil, and the field strength scales with the current and the number of turns. In electric motors, these windings form electromagnets that interact with permanent magnets or other coils to produce torque and rotation.

The other options involve coils or magnetic effects but in different roles. A galvanometer uses a current-carrying coil to sense current by its torque in a magnetic field, not primarily to generate the motor’s driving field. A transformer relies on magnetic flux to transfer energy between windings, which is about energy coupling rather than creating the motor’s drive field. A generator is a device that produces electricity, not the coil arrangement used to create the motor’s magnetic field for motion.