I just purchased my first laptop computer, a Dell Inspiron
N5050 and so far, have been unable to find any information about using the AC
adapter and also about charging the battery in the user manual. Since this is
my first time using a computer with a battery, I have several questions.

The specs say that the battery in my computer is a 6 cell, 48 Watt primary battery. When I first received the computer and turned it on
(running only on the battery at the time), the battery ran down to the point
where the computer would not operate until battery charged in about 2.5 hours.
I assumed that this was because it may have not been fully charged when leaving
the factory or if it had been, the charge may have diminished slightly from
sitting around before and during shipping. 

My first question is how long should I expect this unit to
operate from the time the battery is fully charged until it runs down to the
point where it needs to be recharged? 

Also, the AC adapter which was shipped with the computer is
a 65 Watt, 3 prong adapter, Dell part number MH4Y4. How long should I expect
this adapter to take to fully charge the battery on this system? 

Finally, I noted a number of AC adapters listed for sale
separately on the Dell site, some of them up to 90 Watt. Most if not all of
them say that these adapters permit using the computer via AC power at the same
time that the battery is charging. Can I expect the 65 Watt adapter which came
with the computer to provide this capability of simultaneously charging while
operating the computer? I can’t find anything in the information provided with
the computer or online which discusses this. 

Also, is there any benefit to getting a 90 Watt adapter
instead of using the 65 Watt one which came with my computer? Thanks in advance
for any help.