When a smaller gear drives a larger gear, the result is that the speed

When a smaller gear drives a larger gear, the result is that the speed

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

Answer: (C)

When a smaller gear drives a larger gear, the output speed drops while the output torque rises. This happens because the gear ratio is driven teeth over driving teeth; with the driver having fewer teeth than the driven gear, the ratio is greater than one. The larger gear turns more slowly, but it must deliver more torque to carry the same power, since P ≈ T · ω. For a simple example, a 10-tooth driver and a 20-tooth driven gear give about half the speed and about double the torque. So the correct result is that speed decreases and torque increases.

When a smaller gear drives a larger gear, the output speed drops while the output torque rises. This happens because the gear ratio is driven teeth over driving teeth; with the driver having fewer teeth than the driven gear, the ratio is greater than one. The larger gear turns more slowly, but it must deliver more torque to carry the same power, since P ≈ T · ω. For a simple example, a 10-tooth driver and a 20-tooth driven gear give about half the speed and about double the torque. So the correct result is that speed decreases and torque increases.