What is the difference between AC and DC motors?

What is the difference between AC and DC motors?

• A. DC motors run on direct current (often with brushes) while AC motors use alternating current (induction or synchronous).
• B. DC motors are always faster than AC.
• C. AC motors require brushes; DC motors do not.
• D. Both are identical in operation.

Answer: (A)

The key idea is how the electrical supply drives rotation. A direct-current motor uses DC power and traditionally relies on a commutator and brushes to switch the current in the windings as the rotor turns, delivering steady torque with a DC supply. An alternating-current motor, on the other hand, uses AC power, and the alternating polarity creates a rotating magnetic field in the stator. The rotor either has currents induced in it (induction motor) or is driven to lock into the rotating field (synchronous motor). This distinction is what makes the described pairing—DC motors with direct current (often with brushes) and AC motors with alternating current (induction or synchronous)—the accurate overall differentiation. The other statements aren’t generally true: speed varies with design and control methods, brushes aren’t required for all AC motors, and the two types are not identical in operation.

The key idea is how the electrical supply drives rotation. A direct-current motor uses DC power and traditionally relies on a commutator and brushes to switch the current in the windings as the rotor turns, delivering steady torque with a DC supply. An alternating-current motor, on the other hand, uses AC power, and the alternating polarity creates a rotating magnetic field in the stator. The rotor either has currents induced in it (induction motor) or is driven to lock into the rotating field (synchronous motor). This distinction is what makes the described pairing—DC motors with direct current (often with brushes) and AC motors with alternating current (induction or synchronous)—the accurate overall differentiation. The other statements aren’t generally true: speed varies with design and control methods, brushes aren’t required for all AC motors, and the two types are not identical in operation.