*52%*:**Investigating student understanding of basic quantum mechanics in the context of time-dependent perturbation theory***42%*:**Developing and evaluating an interactive tutorial on degenerate perturbation theory***42%*:**Investigating student difficulties with fine structure corrections to the energy of the hydrogen atom using degenerate perturbation theory***40%*:**Student difficulties with finding the corrections to the energy spectrum of the hydrogen atom for the strong and weak field Zeeman effects using degenerate perturbation theory***38%*:**Investigating Student Difficulties with Dirac Notation***36%*:**Student difficulties with quantum states while translating state vectors in Dirac notation to wave functions in position and momentum representations***34%*:**Student Understanding of Superposition: Vectors and Wave Functions***33%*:**Investigating Student Difficulties with Time dependence of Expectation Values in Quantum Mechanics***32%*:**Analysis of Student Understanding of Statics Principles***32%*:**Surveying students' understanding of quantum mechanics in one spatial dimension***31%*:**Systematic study of student understanding of the relationships between the directions of force, velocity, and acceleration in one dimension***31%*:**Conceptual Understanding of Resistive Electric Circuits Among First-year Engineering Students***31%*:**Investigating the Influence of Visualization on Student Understanding of Quantum Superposition***31%*:**Evaluation of Studentsâ€™ Understanding of Thermal Concepts in Everyday Contexts***30%*:**Investigating student understanding of quantum physics: Spontaneous models of conductivity***30%*:**The Impact of the History of Physics on Student Attitude and Conceptual Understanding of Physics***30%*:**Investigating Student Understanding for a Statistical Analysis of Two Thermally Interacting Solids***30%*:**Developing and validating a conceptual survey to assess introductory physics students' understanding of magnetism***29%*:**Improving Students' Understanding of Quantum Mechanics**