Something that I haven’t been good at is capturing insights during whiteboarding. Sometimes a student asks a really great question that results in a fantastic discussion. Sometimes I have an important question to pose that gets the discussion started. This year, I’m trying to capture this information in my daily reflections so I can consult it in future years. Today’s whiteboard involving a “rail gun” (Giancoli 5e, chapter 20, problem 17) is a great example of this. During my first class, we briefly discussed this problem and moved on. However, during my second class, a student asked about Lenz’s Law and the direction of the current. In this problem, a large current moves in a closed loop which is in an external magnetic field. The light bar experiences a force due to the current in the external magnetic field. The student questioned that the motion should result in an induced current in the opposite direction such that the generated magnetic field would oppose the change in flux. After some pondering, this led to a great discussion of back emf. At least next year, I’ll have this in my notes so all classes can benefit.