What is meant by “friction loss” in a motor?

Friction loss in a motor specifically refers to the energy lost due to the friction encountered in bearings and other moving parts. As components within the motor move against each other or against fixed parts, such as the stator, some of the mechanical energy is transformed into heat rather than being used for useful work. This phenomenon occurs in various parts of the motor, such as bearings, gears, and other mechanical interfaces, where surfaces come into contact.

The loss manifesting as extra heat means less efficiency, as the energy that could have contributed to useful output instead dissipates as unnecessary heat. This understanding is crucial for improving the motor's design and selecting proper lubrication to minimize this friction and enhance overall efficiency. Other options relate to different types of energy losses and do not pertain specifically to the mechanical friction involved in moving parts.