PAT, 3x interviews
SHM inside the earth, reflection of moonlight graph drawing, Taylor expansion, geometry, resolving forces, gravity
Practice interviews, practice problem solving out loud, practice drawing graphs, doing Physics Olympiad and PAT questions out loud
Revision, problem solving
Ask questions or for clarification if you don't understand
Remember this advice isn't official. There is no guarantee it will reflect your experience because university applications can change between years. Check the official Cambridge and Oxford websites for more accurate information on this year's application format and the required tests.
Also, someone else's experience may not reflect your own. Most interviews are more like conversations than tests and like, any conversation, they are quite interactive.
Test taken: Physics Aptitude Test (PAT)
Number of interviews: 3
Time between interviews: They were spread over several days
Length of interviews: 30-60 mins (hard to remember exactly)
Online interview: No
A mixture of maths and physics questions: SHM inside the earth, reflection of moonlight graph drawing, Taylor expansion, geometry, resolving forces, gravity. In general, two interviewers took it in turns to ask questions. I was asked about my personal statement in one and why I wanted to study physics in the other. The interviewers were friendly but it was pretty much 'all business'. My first one went pretty badly because I was nervous but the others were much better because I started to enjoy them. The best way to approach them, in my view, is to remember that they are simulating a tutorial - trying to learn and ask questions and deepen understanding is more important than immediately getting the answer or worrying about getting it wrong. Tutors aren't mind readers, so can't judge aptitude if you don't say anything!
Practice interviews, practice problem solving out loud, practice drawing graphs, doing Physics Olympiad and PAT questions out loud, making sure I knew the syllabus inside out.
Lots of revision. Targeted on areas of weakness from the syllabus and lots of past papers (and practicing under timed conditions). Practice problem solving and doing a little bit every day for several months was also helpful.
Keep talking, try to enjoy it, ask questions or for clarification if you don't understand, be patient with yourself. Breath deeply and try to open up your body language, encouraging your body to feel more confident in its surroundings.