What defines an arc site?

The correct answer identifies an arc site as a specific point on a conductor that shows damage resulting from electrical discharge. This definition highlights the physical evidence left by an electrical arc, which typically occurs when an electric current jumps across a gap, creating a high-temperature plasma and causing thermal damage to the materials involved.

In the context of fire and explosion investigations, identifying an arc site is crucial because it can provide insights into the cause of a fire, especially when evaluating electrical systems' integrity. Evidence of arcing, such as pitting or melting on a conductor, helps investigators understand if a fault or failure in the electrical system contributed to the ignition of a fire.

The other choices do not accurately define an arc site. A general location of electrical installations does not focus on the specific damage indicative of arcing. A place where combustion began refers to the point of ignition without the direct association with electrical discharge. An area affected by heat exposure describes a broader concept of heat damage rather than the specific mechanism and evidence associated with an electrical arc.