If the driven sprocket has more teeth than the drive sprocket, the sprocket ratio is greater than 1.

• A. Less than 1
• B. Equal to 1
• C. Greater than 1
• D. Undefined

Answer: (C)

In a chain drive, the sprocket ratio is set by how many teeth are on the driven sprocket compared with the drive sprocket. The ratio is N_driven divided by N_drive. If the driven sprocket has more teeth, that quotient is greater than 1, so the sprocket ratio is greater than 1.

For example, with a drive sprocket of 20 teeth and a driven sprocket of 40 teeth, the ratio is 2. This means the driven sprocket turns at half the speed of the drive, while the torque on the driven side roughly doubles (ignoring losses). If the driven and drive sprockets had the same number of teeth, the ratio would be 1 (equal speeds). If the driven had fewer teeth, the ratio would be less than 1. The undefined case would be if a sprocket had zero teeth, which isn’t practical.