On AC and battery Windows has a screen brightness setting. NO OS NOTED so all I can note is that's correct operation. You can go on battery power and adjust the screen brightness to your liking.
I have a Dell Inspiron and lately when I unplug my laptop, the screen dims. Battery is new and I never noticed this before. I think I must have changed something related to power conservation or I just haven't noticed it before. Virus scan is clean. Any suggesons are appreciated.