What is the distinction between an arc and a spark?

The distinction between an arc and a spark is primarily rooted in the nature of the phenomena they represent in electrical discharge. An arc refers to a sustained and continuous electrical discharge that occurs when a voltage causes the air (or another medium) to become ionized, allowing current to flow between two points. This is characterized by a visible, glowing plasma channel.

While the answer provided mentions sparks as "thrown metal particles," this is not accurate in the context of electrical discharges. Instead, a spark is a rapid, transient discharge of electricity that occurs between two conductors when the voltage exceeds the dielectric breakdown of the medium between them. Sparks are often short-lived and occur in a single burst, creating a brief flash but not establishing a continuous path for current flow like arcs do.

The correct understanding is that arcs, with their sustained current flow, are often the result of excessive current, making them a more persistent phenomenon compared to the fleeting nature of a spark. This understanding distinguishes the two electrical discharges based on their duration, stability, and the physical conditions that produce them.