The working principle of an emergency light.
the working states of such a device, is that first when there is normal power supply, the lamp does not work, but the battery starts charging.
when the power supply is cut off (occurrence of power failure), then the battery starts powering the lamp.
when the power supply returns, the battery supply to the lamp is cut off, and the battery starts charging again.
now, i want to know what are all the devices present and how exactly they function, in carrying out the above processes.