Which contacts in magnetic contactors are considered normally open (NO)?

• A. Those that are closed when energized
• B. Those that are apart when the relay is de-energized
• C. Those that are connected at all times
• D. Those that open at maximum load

Answer: (B)

In the context of magnetic contactors, normally open (NO) contacts are specifically designed to be open when the contactor is de-energized and to close when the contactor is energized. This functional behavior allows the circuit to remain in a state of non-conductivity until a specific power signal is introduced to energize the contactor.

The choice indicating that normally open contacts are apart when the relay is de-energized correctly describes their operation. By remaining open until the relay receives current, these contacts provide control for various devices, ensuring that power is only supplied when necessary. This is crucial in applications where safety and control are paramount, allowing devices to operate only under intentional conditions.

In contrast, choices that describe contacts as related to them being closed when energized or being connected at all times do not align with the definition of normally open contacts. Normally open contacts must remain open in the absence of energizing power, making their active role contingent on receiving power.