What is described as a high temperature luminous electric discharge across a gap?

The term that accurately describes a high temperature luminous electric discharge across a gap is "Arc." An arc forms when a sufficient voltage is applied across a gap in a conductor, allowing a current to flow as the electrons leap across the gap. This phenomenon generates a significant amount of heat and light, leading to the characteristic luminous appearance of the arc.

Arcing can occur in various electrical systems, including power distribution and welding applications, often indicating a breakdown in insulation or improper connections. Understanding the nature of arcs is crucial in fire and explosion investigations, as they can be a source of ignition in many scenarios. For instance, if a short circuit leads to arcing, it could ignite flammable materials nearby, creating a fire hazard.

The other options—voltage, static electricity, and current—do relate to electrical phenomena, but they do not specifically capture the essence of the luminous discharge across a gap as accurately as "Arc" does. Voltage refers to the electric potential difference, static electricity pertains to stationary electric charges, and current is defined as the flow of electric charge. None of these terms encompass the visual and thermal characteristics of an arc discharge.