In a relay control circuit, what happens to a normally open contact when its controlling coil energizes?

• A. It opens when the controlling coil energizes.
• B. It remains unchanged when the coil energizes.
• C. It closes when the controlling coil energizes, completing the circuit.
• D. It shorts the supply when energized.

Answer: (C)

A relay uses an electromagnet to move a contact. A normally open contact is one that is open when the coil is not energized. When the control coil energizes, the magnetic field pulls the contact together, closing the circuit path and allowing current to flow to the load. This completes the circuit so the load can operate. Once the coil is de-energized, the contact returning to its open state breaks the circuit again. It’s not a short; it’s simply the contact closure that completes the intended path for current.