I've been to many PhD proposals and defenses, but I've yet to give either myself. At every talk I've seen, after the speaker finishes his/her presentation and the non-committee members ask their questions, we're asked to leave the room. I assume the committee then asks the speaker questions.
Are these questions any different from normal questions you would get at a talk or do they function as a sort of impromptu oral exam? Do students prepare for them in a particular way or it is just assumed you'll pick up on what you need from your studies and work on your thesis?