Which factor is indicated as a possible cause for poor insulation resistance in circuit breakers?

Dirt, moisture, and copper collecting internally can significantly impact insulation resistance in circuit breakers. When impurities such as dirt and moisture accumulate within the insulation material, they can create conductive pathways, which lowers the overall insulation resistance. This is particularly problematic in environments where circuit breakers are exposed to contaminants or where humidity levels are high. Moisture can also facilitate corrosion and degradation of insulating materials, further compromising the integrity of the insulation.

In contrast, while other factors like excessive heat, aging of components, and wear and tear on contacts can affect circuit efficiency and longevity, they do not directly relate to poor insulation resistance in the same way that environmental contaminants do. Heat may lead to thermal degradation of materials, aging affects performance over time, and wear can change the physical contact area, yet it is the internal accumulation of dirt and moisture that most directly undermines insulation resistance.