What happens to the lamp in the emergency lighting circuit when the relay is de-energized?

In an emergency lighting circuit, when the relay is de-energized, the typical operation is for the lamp to connect to the storage battery. This is because the primary purpose of such circuits is to provide illumination in the event of a power failure.

When the relay is energized (such as during normal operation when mains power is available), it often disconnects the lamp from the battery to prevent unnecessary drain and keeps it powered via the mains. However, once a power failure occurs, the relay de-energizes, which typically allows for the lamp to receive power directly from the storage battery. This connection is crucial for ensuring that the emergency lighting system operates effectively, providing the necessary illumination when it is most needed.

The design of these circuits ensures that the transition to battery power is seamless, allowing the lamp to turn on and remain lit as soon as the relay de-energizes. Hence, the behavior of the lamp in this scenario is consistent with the expectation of reliable emergency lighting functionality.