Direct current motors are designed for which combination of characteristics?

Direct current motors are designed for which combination of characteristics?

• A. High torque and low inertia
• B. High speed and high inertia
• C. Low torque and high inertia
• D. Constant torque regardless of speed

Answer: (A)

Direct current motors are built to deliver strong starting torque while remaining responsive, which comes from having low rotor inertia. At startup, the motor can draw a relatively large current before back EMF builds up, producing high torque that helps overcome load and friction right from zero speed. Keeping the rotor’s inertia low means the motor can accelerate and change speed quickly for a given torque, improving acceleration and control when loads change. That combination—high torque at startup and low inertia—results in fast, responsive performance, making it the best fit. The other scenarios imply either heavy rotational resistance, insufficient starting torque, or an unrealistic constant-torque behavior that DC motors don’t inherently maintain across all speeds.

Direct current motors are built to deliver strong starting torque while remaining responsive, which comes from having low rotor inertia. At startup, the motor can draw a relatively large current before back EMF builds up, producing high torque that helps overcome load and friction right from zero speed. Keeping the rotor’s inertia low means the motor can accelerate and change speed quickly for a given torque, improving acceleration and control when loads change.

That combination—high torque at startup and low inertia—results in fast, responsive performance, making it the best fit. The other scenarios imply either heavy rotational resistance, insufficient starting torque, or an unrealistic constant-torque behavior that DC motors don’t inherently maintain across all speeds.