i have been typing this out alot and see it asked alot so i fig ild just thread it and be done with it. for the most part your ceiling light and your wall outlets should be on 2 dif breakers. test this by turning on the light and plugging a lamp into the wall and turing off breakers once you have found out if they are on 2 dif breakers turn the breaker back off remove the cieling light and replace it with a receptical box and there u have an added line also i add some hooks up there to manage cords and hang ballast keeping everything above you
I'm not really too sure what you're asking man. Yes, generally lighting and receptacles are on separate circuits. It isn't code, but just good electrical practice. A lot of older home might not be set up like that though. Generally you only want to run 80% of the circuit. Meaning if you have a 15 amp circuit only run 12 amps. If the circuit is for receptacles, you generally account 1.5 amps per receptacle. So, for a 15 amp circuit at 80% is 12 amps divided by 1.5 give you 8 receptacles. I'll go up to 10 receptacles on a 15 amp circuit though if I need too and that is fine. For a 15 amp circuit you can use 14AWG cable (14 gauge).
You can also put receptacles on a 20 amp circuit. Using the same math 80% of 20 amps is 16 amps divided by 1.5 comes out to 10.6 So generally 11-12 receptacles on a 20 amp circuit. I've seen people go up to 15 receptacles for a 20 amp circuit without any problems. It just all depends on where in the house they are and what they will be running. For a 20 amp circuit you need 12AWG cable (12 gauge).
This is good for USA and Canada where we run 120v hot to neutral at 60Hz for household use. Not sure where you are from but from what I understand Europe runs 240V at 50Hz.
Hope this helps. I have a degree in electrical technology so if anyone has any electric questions feel free to msg me.