I'm here to expose what I think is a bug somewhere on the Ubuntu distro.
I recently installed Ubuntu 12.04 on my Samsung N220, following the instruction given by voria on this forum. Everything goes right.
Trying to save energy (and not liking being constantly given microwaves by my laptop), I switched off the wifi. I was surprised to feel that doing this made my battery last less time than with the wifi on and connected to a wireless network.
To make sure it was not just an impression, I installed Powertop (which gives the battery discharge rate in nearly real time). I found out that with the wifi ON and connected, my idle discharge rate was nearly 5.2 Watts, and that with the wifi OFF, my idle discharge rate didn't go under 6 Watts.
That is weird for sure.
To check if it is not a hardware problem, I rebooted using the preinstalled Windows 7. And with windows, the discharge rate is about 5.2 Watts with the wifi OFF, and 6 Watts, with the wifi ON, which seems quite normal to me.
What I did is unload the wifi module on linux (modprobe -r Ath9x) to see what happens : well, with the module unloaded, the discharge rate is still 6 Watts.
I don't know how to explain all this. I thought it was worth reporting it here. Maybe someone would have any idea on how to fix this weird behaviour.
Thank you for your reading and your answers (I hope you will give me any explanations).