Which of the following actions can mechanical power transmission systems perform?

• A. Reverse direction of rotation
• B. Increase friction
• C. Change magnetic polarity
• D. Absorb heat

Answer: (A)

Mechanical power transmission systems are built to move energy from a source to a load while shaping how that energy is delivered, including direction, speed, and torque. Reversing rotation is a practical capability you see in these systems: by arranging gears or belts, the output shaft can rotate in the opposite direction to the input. A simple gear pair automatically reverses direction, and belt drives can reverse direction when the belt is crossed. With multiple stages, the overall direction depends on the number of reversals, but achieving a reverse is a standard capability of mechanical power transmission.

Increasing friction isn’t a designed action of these systems; the aim is to transfer power with controlled, minimal losses. Changing magnetic polarity doesn’t belong to mechanical transmission, since that involves magnetic or electrical phenomena. Absorbing heat isn’t a defined function of a mechanical power transmission system either; heat management is about handling losses, not a primary action the transmission performs.