Installing graphics drivers Ubuntu 13.10(Hybrid Graphics).

If you have hybrid graphics then you don’t have to  turn off the discrete graphic card manually  any more. Ubuntu 13.10 supports hybrid graphics.

AMD Hybrid Graphics : 

I've tested this and it works fine. According to the Ubuntu wiki page there aren't any known issues yet. 
To get proper AMD Hybrid graphics support in Ubuntu 13.10 all you have to do is install the latest fglrx driver and fglrx-pxpress from the repositories.

sudo apt-get install fglrx fglrx-pxpress

with AMD graphics you can switch between the two graphic cards by AMD catalyst control center like you do in Windows. But it requires a system reboot for changes to take effect. Other than that everything is fine. No ever heating.
Here more about this.(if you have a NVIDIA system ).