What symbol indicates that a circuit is energized and should not be approached?

The lightning bolt symbol is widely recognized as an indication of an energized circuit, signaling that it carries high voltage and poses a risk of electric shock or other hazards. This symbol is crucial for safety because it alerts personnel to exercise caution and avoid contact with the circuit. The use of a lightning bolt effectively communicates the danger associated with electricity, making it immediately identifiable and understandable in various settings, particularly in electrical work environments.

Other symbols, while they may indicate caution or danger, do not specifically convey the immediate risk associated with energized electrical circuits. For instance, a warning triangle is often used for general hazards but does not explicitly relate to electrical energy. Similarly, a stop sign is associated with the need to halt or pay attention but lacks the specific context of electrical hazards. A red circle may indicate prohibition or restriction but does not directly inform someone about the dangers of an energized circuit. Thus, the lightning bolt stands out as the most effective and universally understood symbol for indicating that a circuit is energized and should not be approached.