What happens to the resistance in a motor when it overheats?

When a motor overheats, the resistance of the windings typically increases. This phenomenon occurs due to the properties of the conductive materials used in the motor, primarily copper or aluminum. As the temperature of these materials rises, the thermal agitation increases, causing more frequent collisions of charge carriers. This increased motion of electrons leads to a higher resistance.

Additionally, as the motor's temperature elevates, factors like insulation breakdown or changes in the physical structure can further contribute to an increase in resistance. This effect can lead to reduced efficiency and performance, as higher resistance typically translates to increased heat generation under load, potentially resulting in a self-perpetuating cycle of overheating.

In contrast to this, if the resistance were to remain constant, decrease, or become variable under overheating conditions, it would not accurately reflect the standard electrical behaviors observed in conductive materials.