switching between graphics cards and on board graphics in ubuntu

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http://askubuntu.com – Hi I am running ubuntu 12.04 on dell inspiron 14z laptop which has got ATI graphics cards and also intel on board graphics card. By default it uses ATI, which consumes more power and heats up a lot. Is that possible between ATI and on board depending upon our requirement, so that I can save my battery and avoid laptop on heating up? (HowTos)