The amount of thermal energy impressed on a surface at a certain distance from the source of an electrical arc is known as the ?

• A. Incident energy
• B. Arc energy
• C. Thermal energy
• D. Heat flux

Answer: (A)

Incident energy describes the amount of thermal energy impressed on a surface at a specific distance from an arc source. It quantifys the energy per unit area that would be delivered to that surface during an arc flash, usually expressed in units like cal/cm^2 or J/m^2. This concept is what engineers use to assess hazard and determine PPE and protective boundaries, because it directly relates to the thermal dose the wearer or surface would receive. Heat flux, by comparison, is the rate at which energy arrives per unit area (energy per time per area), so it tells you how intense the heat is at an instant rather than the total energy delivered. Arc energy isn’t a standard term in this context, and thermal energy alone doesn’t specify the delivered energy at a distance.