11.10 - How do I know which graphics card is being used in a hybrid system?

I have an Acer Aspire 5935G. It comes with hybrid grahics solution from Nvidia. It has two graphic cards; Nvidia GeForce 130GT M (discrete) and Intel mobile graphics series 4. I have just installed Ubuntu 11.10 but I get no information about what graphics card the notebook is currently using. Also how can I use only one of them permanently (preferably Intel graphics), while disabling the other?