The three basic components of a gear drive system.

• A. Driven gear, Idler gear, Master gear
• B. Driver gear, Driven Gear, Idler gear
• C. Driver gear, Idler gear, Driven Gear
• D. Gear teeth only

Answer: (B)

In a gear drive system, the three basic components are the driver gear, the driven gear, and an idler gear. The driver gear is the gear attached to the power source and does the work of turning. The driven gear is the one connected to the output load and receives the motion and torque. The idler gear sits between the driver and driven gears to change the direction of rotation or to adjust center distance and spacing; it doesn’t change the gear ratio on a single-idler setup.

The speed and torque relationship (the gear ratio) comes from the teeth counts of the driver and driven gears themselves. An idler doesn’t alter that ratio by itself — it just redirects motion. If multiple idlers are used, the ratio is still determined by the first and last gears in the train.

That’s why the option listing driver gear, driven gear, and idler gear is the standard, correct trio. Other choices either omit the driver or use nonstandard terms like “master gear,” or reduce the set to gear teeth only, which doesn’t describe the functional roles involved.