This is an interactive tutorial for introductory physics on resistance and Ohm's Law. It explores the journey of an electron through the wires of an electric circuit, explaining how countless collisions between the charge carriers and atoms within the wires result in loss of electrical energy. In the second part of the tutorial, students learn about factors affecting resistance, resistivity values, and how to calculate resistance mathematically. This page is part of The Physics Classroom, a comprehensive set of interactive tutorials, labs, and simulations for students of introductory physics. The Physics Classroom is one of the ComPADRE digital library collections.