Which statement correctly describes the effect of increasing gear ratio on motor output?

• A. It increases output speed and decreases torque.
• B. It decreases both speed and torque.
• C. It increases torque and reduces speed.
• D. It increases speed but does not affect torque.

Answer: (C)

Increasing the gear ratio means more reduction in speed and more leverage at the output. In a gear train, higher reduction sends the motor’s rotation through more gear teeth, so the output shaft spins more slowly but with greater torque. Ignoring losses, the output torque scales with the ratio while the output speed scales inversely with it: speed_out ≈ speed_in / gear_ratio and torque_out ≈ torque_in × gear_ratio. This trade-off lets the robot handle heavier loads or start under load, at the cost of slower motion. For example, a 4:1 reduction would roughly quarter the output speed while roughly quadrupling the available torque (minus efficiency losses). The other statements describe scenarios that contradict this fundamental trade-off: increasing speed with higher reduction, or decreasing both speed and torque, or increasing speed while leaving torque unchanged.