What is a common use of PWM in motor speed control?

• A. To stabilize the supply voltage
• B. To increase motor torque at all times
• C. To simplify wiring
• D. To adjust motor speed by varying the average voltage delivered.

Answer: (D)

PWM controls motor speed by adjusting the average voltage delivered to the motor. It switches the power on and off rapidly, and by changing the duty cycle—the fraction of time the voltage is on in each cycle—you change the overall average voltage the motor experiences. The motor’s inertia smooths these pulses, so its speed follows that average voltage. This lets you fine-tune speed efficiently without wasting energy as heat like a linear regulator. The other ideas aren’t what PWM is doing here: it’s not mainly about stabilizing a supply voltage, it doesn’t guarantee more torque at all times (torque depends on current and load), and it doesn’t inherently simplify wiring.