Generally how many questions should you ask on your interview?
And what does these question revolve around?
The program itself, or maybe postgradrate program?
Just ask what you want to know more about.
For myself, I wanted to know how their patient flow was and if there were patients from different socioeconomic backgrounds.
Ask as many questions as you think is appropriate. You get to find out more information about the school that isn't in the brochures. AND it keeps the interviewers from asking questions! Win-win!