Oilers/Plant Tenders (HHC) Civil Service Practice Exam

Which type of bearing is NOT commonly used in most electric motors?

1. Ball bearing

2. Roller bearing

3. Gibbs thrust bearing

4. Sleeve bearing

The correct answer is: Gibbs thrust bearing

The correct choice identifies a Gibbs thrust bearing as not commonly used in most electric motors. The reason this is accurate is that while electric motors require bearings for rotating components, they typically utilize designs that best accommodate the needs of motor operation, such as load capacity, friction levels, and speed. Ball and roller bearings are prevalent in electric motors due to their efficiency in handling radial and axial loads. Sleeve bearings are also frequently employed in motors, especially in applications where quiet operation and low friction are prioritized. On the other hand, Gibbs thrust bearings are specialized bearings designed primarily for heavy axial loads in specific applications, but they are not a standard choice for electric motor designs which focus on rotational and vibration management. This distinction is crucial for understanding the types of bearings suitable for different applications, particularly in the context of electric motor design and function.