What is the most likely cause of electric motor failure?

Moisture is a prevalent cause of electric motor failure for several important reasons. It can lead to the corrosion of internal components, creating a conductive pathway that increases the risk of short circuits. When moisture accumulates in or around an electric motor, it can interfere with electrical connections and insulation, ultimately leading to equipment malfunction. Additionally, if moisture gets into the bearings or other moving parts, it can cause rust and impede mechanical performance, leading to further degradation and potential failure of the motor.

In the context of the other choices, while dust can cause overheating or blocking air flow, it is not as significant a threat to electrical components as moisture. New connections could introduce potential issues if improperly installed, but they do not inherently lead to failure. Lack of friction is typically undesirable in mechanical systems because it may indicate insufficient lubrication rather than a direct cause of motor failure. Understanding these nuances highlights why moisture is a critical factor in maintaining electric motors and preventing their failure.