What is gear ratio and how does it affect torque and speed?

• A. Gear ratio is the relationship between input and output speeds; higher ratios decrease torque.
• B. Gear ratio only affects efficiency and has no impact on torque.
• C. Gear ratio is the relationship between input and output speeds; higher ratios increase torque and reduce speed.
• D. Gear ratio refers to the size of the gears only.

Answer: (C)

Gear ratio describes how the input speed is transformed to the output speed and how the available torque changes as a result. When the gear ratio is higher, the output spins more slowly but delivers more torque. This happens because power must be roughly conserved (ignoring losses): output torque times output speed ≈ input torque times input speed. Using a smaller driving gear and a larger driven gear increases the ratio, giving more torque at the slower output. The opposite setup yields higher output speed but less torque. So the statement that higher ratios increase torque and reduce speed matches this speed-torque trade-off. The other ideas—that ratio only affects efficiency, or that it’s just about gear size—don’t capture the fundamental relationship between speeds and torque.