The advantage of a DC motor is its ______ can be easily controlled.

The advantage of a DC motor is its ______ can be easily controlled.

• A. Torque
• B. Speed
• C. Power
• D. Efficiency

Answer: (B)

Speed is the aspect of a DC motor that you can tune most directly. The rotation rate responds primarily to the voltage you apply: increasing the supply (or using a PWM signal to raise the effective voltage) makes the motor run faster, while lowering the voltage slows it down. This is because the motor’s back-EMF (a voltage generated by the spinning rotor) increases with speed and acts to oppose the applied voltage; the balance between the applied voltage and back-EMF determines the current and thus the speed under a given load. In practice, speed control is achieved precisely by adjusting voltage or duty cycle, providing fast and wide-ranging control. Torque, on the other hand, is tied to the current through the windings, so it requires current regulation to set accurately. Power depends on both speed and torque, so it isn’t a single adjustable parameter by itself. Efficiency varies with operating conditions and losses and isn’t something you “set” directly.

Speed is the aspect of a DC motor that you can tune most directly. The rotation rate responds primarily to the voltage you apply: increasing the supply (or using a PWM signal to raise the effective voltage) makes the motor run faster, while lowering the voltage slows it down. This is because the motor’s back-EMF (a voltage generated by the spinning rotor) increases with speed and acts to oppose the applied voltage; the balance between the applied voltage and back-EMF determines the current and thus the speed under a given load. In practice, speed control is achieved precisely by adjusting voltage or duty cycle, providing fast and wide-ranging control.

Torque, on the other hand, is tied to the current through the windings, so it requires current regulation to set accurately. Power depends on both speed and torque, so it isn’t a single adjustable parameter by itself. Efficiency varies with operating conditions and losses and isn’t something you “set” directly.