The Princeton University Preliminary Examinations are a set of exams to be taken by all Princeton University graduate students. The exams are offered every year on January and May, although in the past they have also been offered in October. Every graduate student at Princeton gets at least two chances to pass these exams, and everyone should pass it by the end of their second year. The exam has four sections: Classical Mechanics, Electromagnetism, Quantum Mechanics and Statistical Mechanics. Each of these sections contains three problems, of which the student needs to solve two, and the passing grade is said to be 50% of that (though no faculty member will confirm this). A list of all problems that appeared on prelims in the past exists online, but there is currently no compact website with the answers, except for this wiki system.
Solutions to the problems