Students generally take the preliminary examination in January or May of their first year.
The preliminary exam consists of four sections: mechanics; electricity and magnetism (E&M); quantum mechanics; and thermodynamics and statistical mechanics (TSM). Each student must complete two of the three problems given in each section. The exam is given on two consecutive mornings, with mechanics and E&M on the first day, and quantum and TSM on the second day.
No calculators or other electronic devices or other assistance may be used during the exam. The solution to each problem is to be written in a separate exam booklet, so each student turns in four exam booklets at the end of each day's 3-hour exam session. The faculty grade the exam booklets and then meet to determine which students have passed the exam.
It is necessary to study for the prelims. There are prelims-prep courses offered in the fall. Student-formed study groups are an effective preparation tool.
Links to previous years' exams are below:
Possible other useful study aid can be found here