What occurs after the coil of an on-delay timing relay is energized for a pre-programmed period of time?

When the coil of an on-delay timing relay is energized, it begins to track time for a pre-programmed duration. During this initial phase, the relay does not activate its contacts immediately. The function of the relay is to delay the operation of its output contacts until the set time elapses. Therefore, after the designated time has passed, the normally open (NO) contacts close, allowing current to flow through them, while the normally closed (NC) contacts open, interrupting any current flow.

This behavior is essential for applications where a delay in operation is needed, for example, to prevent rapid cycling of equipment or to wait until certain pre-conditions are met before activating a load.

The other choices do not accurately reflect the operation of an on-delay timing relay. For instance, the closure of NO contacts or the opening of NC contacts happens after the set time, not immediately when the relay coil is energized. Understanding this operation is crucial for effectively utilizing on-delay timing relays in electrical circuits.