Incident energy is defined as the thermal energy impressed on a surface at a distance from the arc source during an electrical arc event. Which statement best defines incident energy?

• A. Electrical energy at the source
• B. Thermal energy impressed on a surface at a distance from the arc source
• C. Magnetic energy due to current
• D. Heat generated by environmental conditions

Answer: (B)

Incident energy is the heat actually delivered to a surface from an electrical arc, measured at a distance from the arc source. It describes the thermal energy impressed on that surface during an arc event, not the energy generated at the source, not magnetic energy, and not heat from environmental conditions. This heat dose is what arc-flash evaluations use to determine exposure and PPE requirements, typically expressed in cal/cm^2 or J/cm^2 and influenced by arc duration, distance, and enclosure. The definition that matches incident energy is the thermal energy impressed on a surface at a distance from the arc source.