In a single-line electrical diagram, what does a normally open contact indicate when the actuator is not energized?

In a single-line electrical diagram, what does a normally open contact indicate when the actuator is not energized?

• A. It remains closed when not energized.
• B. It open only when energized.
• C. It closes when energized.
• D. It is open; it closes when energized.

Answer: (D)

A normally open contact is open when the circuit is not energized, and it closes when the actuator is energized. In a single-line diagram, the NO symbol shows a gap in the unenergized state; energizing the coil pulls the contact closed, completing the circuit. So, when the actuator is not energized, the path is open, and it only closes upon energization. This distinguishes it from a normally closed contact, which is closed when not energized.

A normally open contact is open when the circuit is not energized, and it closes when the actuator is energized. In a single-line diagram, the NO symbol shows a gap in the unenergized state; energizing the coil pulls the contact closed, completing the circuit. So, when the actuator is not energized, the path is open, and it only closes upon energization. This distinguishes it from a normally closed contact, which is closed when not energized.