How many bearings do all electric motors require, and where are they mounted?

• A. Two, externally
• B. Two, internally
• C. One, internally
• D. Three, internally

Answer: (B)

Shaft support and alignment are the key ideas here. Electric motors rely on bearings to let the shaft rotate smoothly while staying properly aligned with the stator. In almost all motors, there are two bearings, one at each end of the shaft, and they are mounted inside the motor housing (in the end bells). This internal placement provides balanced radial support and prevents endplay, keeping the rotor centered during operation.

Having two bearings is important because a single bearing wouldn’t adequately control end movement or resist loads from both directions; it would allow wobble and misalignment, leading to vibration and wear. The internal mounting keeps the bearings protected and lubricated as part of the motor’s sealed design.