Sparking from the [flash] socket when connecting laptop adapters.

Hello.
From time to time, when connecting the laptop adapter to the socket in the socket there is a sudden sparking and exactly a short flash in the socket.
I checked in other sockets and it is the same.
On a different power supply from the second laptop is the same.
The wires in the sockets are firmly twisted and there are no looseness.
I checked other devices, e.g. a hair dryer, and nothing like that happens.
Only on laptop adapters. This is not sparking but a very short flash in the socket when inserting the plug.

Is this a normal phenomenon?

Yes, normal phenomenon.

And why is this done?

Because the capacitor in the charger must charge and suddenly accumulates a large electric charge in a short time.

Thanks for the help.