Oklahoma Electrical Practice Exam

What factor determines the ampacity of a wire in a conduit at ambient temperature?

1. Wire insulation rating

2. Conduit diameter

3. Number of conductors

4. All of the above

The correct answer is: All of the above

The ampacity of a wire, which refers to the maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration, is influenced by several interconnected factors. The wire insulation rating is crucial because it dictates the thermal limits of the wire and how much heat it can safely withstand. Different materials have varying thermal properties, impacting the wire's ability to dissipate heat generated by electrical current. Conduit diameter is another determining factor because it affects the heat dissipation of the wires inside. A larger conduit can allow for better airflow and cooling, which helps maintain lower temperatures and thus may increase the ampacity. Additionally, the number of conductors within a conduit also plays a significant role. As more conductors are placed together, they can produce more heat due to mutual heating effects, which can reduce the overall ampacity if not properly accounted for. Considering all these aspects—insulation rating, conduit diameter, and the number of conductors—it becomes clear that the ampacity is influenced by a combination of these factors, validating the choice that all of them together determine the ampacity of a wire in a conduit at ambient temperature.