What is the fourth listed advantage of AC motors over DC motors?

What is the fourth listed advantage of AC motors over DC motors?

• A. Less Weight
• B. A readily available power supply
• C. Cheaper
• D. Maintenance Cost

Answer: (A)

The main idea is that AC motors, especially induction motors, use a much simpler rotor and don’t rely on a commutator or brushes. The rotor is a lightweight laminate with bars (a squirrel-cage design) and everything heavy in the motor is concentrated in the stator windings. Since there’s no rotor winding, no brushes, and no commutator to accommodate, the moving part that has to carry current and wear is inherently lighter. For a given power output, that simpler, brushless rotor construction generally allows the motor to be built with less mass, which is why weight is often cited as a notable advantage of AC motors over DC motors and can appear as the fourth listed benefit. The other advantages—ease of power supply, cost, and maintenance—are real but don’t hinge on this rotor simplification in the same way.

The main idea is that AC motors, especially induction motors, use a much simpler rotor and don’t rely on a commutator or brushes. The rotor is a lightweight laminate with bars (a squirrel-cage design) and everything heavy in the motor is concentrated in the stator windings. Since there’s no rotor winding, no brushes, and no commutator to accommodate, the moving part that has to carry current and wear is inherently lighter. For a given power output, that simpler, brushless rotor construction generally allows the motor to be built with less mass, which is why weight is often cited as a notable advantage of AC motors over DC motors and can appear as the fourth listed benefit. The other advantages—ease of power supply, cost, and maintenance—are real but don’t hinge on this rotor simplification in the same way.