*45%*:**Contrasting studentsâ€™ understanding of electric field and electric force***40%*:**Longer term impacts of transformed courses on student conceptual understanding of E&M***39%*:**Student Learning In Upper-Level Thermal Physics: Comparisons And Contrasts With Students In Introductory Courses***38%*:**Improving Student Understanding of Vector Fields in Junior-Level E&M***38%*:**Student Objections to and Understanding of Non-Cartesian Unit Vector Notation in Upper-Level E&M***38%*:**Student understanding of Symmetry and Gauss's law***37%*:**E&M Tutorial III: Distinguishing between the electric field & electric flux***37%*:**E&M Tutorial IV: Exploiting Gauss's Law to Find the Magnitude of the Electric Field***37%*:**E&M Tutorial V: Revisiting the Superposition Principle after Gauss' Law***37%*:**E&M Tutorial VI: Exploring symmetry to calculate the electric field using Gauss's Law***35%*:**Tapping into Juniorsâ€™ Understanding of E&M: The Colorado Upper-Division Electrostatics (CUE) Diagnostic***35%*:**Peaks and decays of student knowledge in an introductory E&M course***35%*:**Probing Student Understanding with Alternative Questioning Strategies***34%*:**Addressing Students' Difficulties in Understanding Two Different Expressions of Gravitational Potential Energy (I): mgh & -GMm/r***33%*:**Student understanding of symmetry and Gauss's law of electricity***33%*:**Writing Position Vectors in 3-d Space: A Student Difficulty With Spherical Unit Vectors in Intermediate E&M***31%*:**Improving Student Understanding of Coulomb's Law and Gauss's Law***31%*:**A Longitudinal Study of the Impact of Curriculum on Conceptual Understanding in E&M***31%*:**Investigating Student Understanding for a Statistical Analysis of Two Thermally Interacting Solids**