Industrial shafts transfer power, torque, and movement from one machine to another, from human to machine, or from machine to its end use.

• A. Energy
• B. Torque
• C. Power
• D. Force

Answer: (B)

Torque is the twisting action that a shaft transmits to create rotation. In an industrial drive, the shaft carries rotational motion from a motor or another source to the driven equipment, and the quantity that actually causes that rotation is the torque—the moment about the shaft’s axis. Power is related but different: it’s the rate at which work is done and equals torque multiplied by angular speed. Energy is the capacity to do work, and force is a linear push or pull; neither is the direct quantity transmitted through a shaft in rotational power transmission. So the shaft’s fundamental job is to transfer the twisting moment, making torque the best choice.