Final answer:
While the exact ampacity cannot be determined without the NEC temperature correction factor tables, typically the base ampacity for the conductor is adjusted using these tables for high-temperature environments. The example calculation provided explains how to determine the temperature rise from a short circuit by calculating the power dissipated, the total energy, and applying the specific heat capacity formula.
Step-by-step explanation:
Ampacity Calculation in High Temperature Environments
The question asks for the ampacity of two #12 THW conductors in a raceway at an ambient temperature of 115°F. Unfortunately, without additional context like the temperature correction factors from the National Electrical Code (NEC) tables, a precise answer cannot be provided. Typically, you would look up the base ampacity for a #12 THW conductor and then apply the appropriate correction factor for the higher temperature environment to adjust the ampacity accordingly.
As for the example question provided, it is related to a short circuit in a 120-V appliance cord that has a 0.500-ohm resistance. We would calculate the temperature rise of the 2.00 g of material using the power dissipated (P = V2/R), the specific heat capacity provided, and the duration of the current until the circuit breaker interrupts.
For educational purposes, here is how the calculation would work:
Calculate the power dissipated during the short circuit: P = V2/R
Determine the total energy dissipated: Energy = Power × Time
Apply the specific heat formula: ΔT = Energy / (mass × specific heat capacity)
This will give you the temperature rise which can help determine if the short circuit will be damaging to the surrounding materials.