Kind of depends on what the expectations are for students at your school. If you are expected to preround (ie see patients and write notes before the residents do) your hours will be longer on any rotation. It also depends what time you are expected to have your notes done by.
So when I was on medicine, I got to the hospital by about 6:30, and left at about 5 unless we were on call. Students take overnight call, so how much sleep you get depends on how busy the service is and how many admissions you get. Then we had to put in the full day post call as well.
Surgery last year I had to get in earlier, as we were seeing more pts and had to have notes done before OR time at 7:30. So I'd arrive at 5:30ish. We'd leave between 6 - 8 pm (varied depending on how busy the service is and how efficent the residents, esp the chief is) or so, again, unless you are on call, in which case you may or may not be up all night and then put in the full day the next day. WE also did some trauma, which was 24 hours on/24 hours off
Having said that, those were my hours last year. These new work hour regulations have affected all services, and most of them are experimenting with new schedules this year in order to be in compliance last year. That then trickles down and affects student schedules. (eg no more q2 call) it's still a work in progress, some services have changed scheduling again becuse the first new plan didn't work well. This year is definitely a transition year in terms of schedule.