In a ladder diagram, what does a normally open contact represent?

• A. A contact that opens when energized.
• B. A contact that closes when energized.
• C. A contact that is closed at all times.
• D. A coil that energizes the circuit.

Answer: (B)

In ladder diagrams, a normally open contact acts like a switch that is open at rest and closes to complete the circuit when the controlling input is energized. When the input energizes, the contact closes and current can flow through the rung to energize the next device or coil. This is why it’s described as closing when energized. This differs from a normally closed contact, which is closed when not energized and opens when energized. A coil, on the other hand, is the output device that gets energized, not a contact.