Compared with spur gears, worm gears generally exhibit what characteristics in efficiency and heat generation?

• A. Lower efficiency and more heat due to sliding
• B. Higher efficiency and less heat
• C. Equal efficiency but more noise
• D. Lower torque capacity

Answer: (A)

The main idea is how the two gears make contact. In a worm gear, the engagement between the worm and the worm wheel involves a long, sliding interface. This sliding friction is relatively high and persists along the contact path, so a larger portion of input power is lost as heat. Spur gears, by contrast, mesh with teeth that mostly roll past each other, with far less sliding friction, leading to lower losses and higher efficiency. So worm gears generally run with lower efficiency and more heat generation than spur gears. Lubrication helps reduce losses but doesn’t eliminate the inherent sliding friction. The other statements don’t match this fundamental difference in how the contact operates.