Laptop heats on AC power

my vaio laptop base get really hot when i run it through ac power i.e adaptor on the other hand when i am running on battery temp remains at sane level why this happens

its not the battery which is heating a small area of just 3"x3" near the cpu gets more hot,most of the time my battery is at 100% so its not charging but still it gets more hot on ac power,why this happens?

no, on both battery and ac i have selected high performance plan but still it get more hot on ac whyyyyyyyyyyyyyy

Normally when you plug in your laptop the processor goes into a higher stepping and gives you better performance. Laptop manufacturers generally reduce your processors maximum speed when on battery power, this in tern reduces heat ill put it into something you can relate to.

My processor in my laptop (HP Envy 15) a i7 runs at 15Watts when on battery mode no matter the power option I set in windows aka Power saver or Maximum Performance, and the heat generated is also lower - with the trade off of lower maximum performance. The cpu multiplier goes to a max x7 setting or 950odd Mhz.

When plugged in, I get well over that multiplier rating, x20 giving me the max turbo boost rating of 2.6 Ghz. Again despite what I set in my power options, although power saver will limit the multiplier when plugged in.

Higher Multiplier = Faster Processor = More Heat

The lower multiplier on battery also helps to extend battery life because the firmware within the laptop will physically not allow the CPU to go above 950 Mhz.

I hope this helps.

I use a laptop cooler to remove the issue.

The battery charging doesn't really create any heat, my laptop stays prity cool unless I'm really utilising the processor, I'm in agreement that charging while using your laptop will add to the heat generated, but 95% of the heat is going to be through the utilization of processor, GPU hard disks etc.

If your laptop is plugged in, it will run faster because its able to draw more power as there is no requirement to preserve battery life, and thus will run way hotter, I can very much notice the difference.