Hi Sophie and welcome to Apple Discussions,
I do not know where you found out that this is normal. I have never had a charger spark when plugged in.
If it is only 5 days old unplug it and stop using it and go to a Genius Bar and have it checked out under your Apple Care.
I would worry about it damaging the computer not the charger.
I have just reread your question.
Do you mean that the charger sparks when you plug it into the wall socket or when you plug the other end into your computer.