What is a key difference between AC and DC motors?

• A. AC motors use direct current while DC motors use alternating current
• B. DC motors provide better speed control compared to AC motors
• C. AC motors are less efficient than DC motors
• D. DC motors do not require a commutator, while AC motors do

Answer: (B)

The key reason why better speed control is a defining characteristic of DC motors lies in their operational principles. DC motors can easily vary their speed by adjusting the voltage applied to them or by changing the winding configuration, allowing precise control over torque and speed. This is particularly useful in applications where varying speed is essential, such as in electric vehicles and robotics.

On the other hand, while AC motors can also vary their speed, it typically involves more complex methods such as using variable frequency drives (VFDs) or changing the supply frequency, which may not offer the same level of simplicity in speed control that DC motors can achieve.

The other options involve misunderstandings or inaccuracies about the characteristics of AC and DC motors. For instance, AC motors actually operate using alternating current, while DC motors use direct current, which is the opposite of what is stated in other choices. The efficiency of AC motors can vary widely based on design, and some AC motors can be quite efficient, challenging the claim that they are generally less efficient than DC motors. Lastly, both motor types have different construction features: DC motors require commutators to convert DC into rotational motion, unlike most AC motors, which do not use commutators. Thus, the aspect of speed control is a