In a magnetic normally open (N.O.) contactor, when is the circuit closed?

• A. When the control voltage is above 5V
• B. When the movable contact makes contact with the stationary contact
• C. When the coil is disconnected
• D. When the current is interrupted

Answer: (B)

In a magnetic normally open (N.O.) contactor, the circuit is closed when the movable contact makes contact with the stationary contact. This occurs as a result of energizing the contactor's coil, which creates a magnetic field that pulls the movable armature toward the stationary contact, thus forming a connection between the two. This allows electrical current to flow through the circuit that the contactor controls.

The functioning of an N.O. contactor is designed to facilitate or interrupt the flow of electricity based on the control signal applied to the coil. While other options mention different scenarios regarding voltage levels, disconnection, or current interruptions, they do not accurately represent the point at which the contactor actively closes the circuit. The defining action for closing the circuit in this specific type of contactor hinges solely on the physical contact made between the movable and stationary components when the coil is energized.