What is defined as a short circuit?

A short circuit is defined as a circuit that has an unintended low-resistance path, allowing current to flow along an unexpected route. This typically occurs when electrical connections are made inappropriately, such as when wires accidentally touch each other or when insulation is worn away, leading to a direct connection between different points in the circuit.

In this situation, the low-resistance path enables a much larger current to flow than the circuit was designed to handle, which can cause overheating, damage to components, or even fires. The term "short circuit" essentially refers to the "shortening" of the path that the electrical current must take, bypassing the normal load or resistance that would limit the current flow.

The context of this definition clarifies why other choices do not fit the concept of a short circuit. A circuit with no resistance is a theoretical concept but does not describe the real-world implications of a short circuit. A circuit that only operates intermittently does not capture the consistent risk and potential hazards associated with a short circuit. Lastly, a closed circuit with high resistance would not facilitate the conditions necessary for a short circuit, since high resistance limits current flow significantly rather than enabling excessive current.