hotter when plugged in

I had planned to use it plugged in most of the time but it is alot hotter when plugged in so I use the battery until it gets low.
Is this normal?

 

Yes, it is like, when it is in battery it use less power [in vista it cut by default the cpu use to 50% max], but heavily application will work less fast. Try enconding a video, check the times, maybe it is like this.

 

If you're planning on using it stationary on your desk, you should use the power plug even though it may get hotter. The reason for getting hotter is definetly more cpu-power being used, which actually is quite good... I wouldn't use the battery at all when using a laptop stationary. Recurring loading cycles and the heat make your battery become weaker and weaker. As you will need the battery when using the aa1 as a mobile device you'll get mad for having stressed your battery in situations you didn't even needed it.

So my solution ever was to use the battery in mobile situations and taking it out of the device when using it fully stationary. Also charging the battery only when it's fully discharged raises its lifetime!