How is gear ratio defined?

Gear ratio is defined as the ratio of the number of teeth on the driven gear to the number of teeth on the driving gear. This definition highlights the relationship between the gears in a mechanical system, specifically how they interact to transmit power and motion. When one gear (the driving gear) turns, it causes the other gear (the driven gear) to turn as well, and the ratio of the teeth directly affects the mechanical advantage and speed variation in the system.

For instance, if a driving gear has 10 teeth and the driven gear has 20 teeth, the gear ratio would be 1:2. This means that for every complete turn of the driving gear, the driven gear will turn half a turn. Therefore, the gear ratio is crucial in determining how torque and speed are transformed within a mechanical system, impacting the overall functionality of machines and devices.

The other options do not accurately capture the definition of gear ratio. While size and distance moved could relate to gear operation in different contexts, they do not specifically define the ratio in terms of teeth numbers, which is essential for understanding gearing mechanics.