Which statement describes the effect on speed and torque when a smaller gear drives a larger gear?

• A. Speed increases and torque decreases
• B. Speed decreases and torque increases
• C. Speed increases and torque increases
• D. Speed decreases and torque decreases

Answer: (C)

When a smaller gear drives a larger gear, the gear ratio causes the driven gear to rotate more slowly while needing more turning force. The larger gear has more teeth, so each turn of the smaller driver pushes the larger gear through a larger arc but with fewer revolutions overall. To keep the power transfer similar (ignoring losses), the torque on the driven gear must rise as the speed drops. For example, if the driver has half as many teeth as the driven gear, the driven gear’s speed is about half, and its torque is about twice, neglecting losses. So the correct description is that speed decreases and torque increases.