Although I am not in position to talk about what qualifying exams really feel like, I can tell you that the quals are a major milestone towards a PhD. Not only that, but most quals formats can fall into two categories: comprehensive exams about everything you learned prior or the defense of a research prospectus. Both formats can be quite terrifying. There are those departments where quals can be skipped under certain conditions, however.
- Comprehensive exams. There are those departments where the tests cover the basic material (in physics, there is typically one test on classical mechanics and on electromagnetism, one test on quantum mechanics and on statistical mechanics, but sometimes there are other tests sprinkled in as well) where the objective is to know whether one actually knows the material required to move on to the dissertation. Example department using this format: University of North Carolina physics and astronomy
- Research prospectus defense. Here one has to do a literature review of one’s intended dissertation research, as well as to identify a working hypothesis and the aims of the research. The objective is therefore to assess the familiarity of the student with the research in the field, and its knowledge thereof. Example department using this format: Vanderbilt physics and astronomy
- Quals with conditional waivers. Departments where one can, in whole or in part, waive quals under certain conditions. Take Tufts’ physics and astronomy department, for example. One can waive one of the tests if the grade in the corresponding course(s) is A- or better.
- No quals at all. This might surprise you but there is that rare department where there are no quals at all. Starting in 2014, the University of Chicago physics department decided to phase out the quals.
Addendum: Here’s a quote pertaining to the University of Chicago physics department choosing to phase out the quals from a current University of Chicago physics PhD student that prefers not to be named:
Starting in 2014, the candidacy exam in the University of Chicago physics PhD program is pretty much cancelled. Instead, you take a placement exam upon arriving, and then a counseling committee decides which courses you need to take, based on your performance. You are qualified once you pass the courses they tell you to take.
Apparently, the faculty wishes to make the qualifying process less stressful by this new system.
And, unless phasing out the quals is also something the astronomy department will do in the near future (due to some administrative action), it looks like its astronomy department students go through what amount to three dissertation defenses, each of which are increasing in scope. And the first two defenses would, together, comprise the equivalent of quals.