How do Form B contacts operate?

Form B contacts are defined as normally closed contacts. This means that in their default state, when no external force or current is applied, these contacts remain closed, allowing electricity to flow through them. This characteristic is important in control circuits and safety devices, allowing for a current pathway until a device is activated or a condition changes.

When a Form B contact is energized, it opens, interrupting the circuit. This design is commonly utilized in situations where a disruption or shut-off of power is required to indicate an alarm or failure condition, ensuring that power is maintained during normal operation and only interrupted when necessary.

The other options suggest configurations that do not align with how Form B contacts are designed to function. Normal operation is critical for understanding circuit behavior and design continuity, emphasizing the importance of Form B's normally closed nature in various applications.