Journeyman Electrician Practice Exam

When determining ampacity, what is the relationship between the number of conductors in a conduit and the ampacity rating?

1. More conductors decreases ampacity

2. More conductors has no effect on ampacity

3. More conductors increases ampacity

4. A single conductor has the highest ampacity

The correct answer is: More conductors decreases ampacity

The relationship between the number of conductors in a conduit and the ampacity rating is based on the principle that as the number of conductors increases, the heat generated by electrical current also increases. This is due to the fact that multiple conductors can lead to a buildup of heat within the confined space of the conduit, restricting their ability to dissipate heat effectively. Consequently, to prevent overheating and ensure safety, the ampacity of each individual conductor must be reduced when there are multiple conductors in the same conduit. Ampacity ratings are determined under standard conditions, typically based on one conductor being installed in open air. When additional conductors are present, these conditions change, necessitating adjustments to the ampacity to account for increased thermal loading. Thus, means that more conductors will lead to a decrease in the effective ampacity due to these factors, ensuring that electrical systems operate safely and efficiently.