Today's class, suggestions on how to prepare for class, capacitors and energy in electric fields

One of the keys to preparing for a class, in my opinion, is to review what came before. If you spend 15 minutes reviewing and thinking about the last class, that can enhance what you learn and remember each day.  Additionally, you can let that provide a basis for thinking about what might come next. Even if what you think of is not correct, it takes you out of a passive mode and into a more active, thinking mode, which will probably help your learning.

For example, on Friday we looked at capacitors. We began with the ansatz that the electric field between the plates of a capacitor does not depend on x, the position inside the capacitor.  We then showed that the potential, V(x),  does depend on x.  Finally we noticed that the difference between  the potential at one capacitor plate and the other capacitor plate is proportional to Q,  the magnitude of the charge on either one of the capacitor plates.  This potential difference is known as the voltage, V. ( We called it delta V in class.)  One can put that another way: the charge on the capacitor, Q,  is proportional to the voltage, V.  We call this proportionality the capacitance, C, and we thus write Q=CV.  (What does C depend on?)

Next class, today, we will look at the difference in energy between a charged capacitor and a uncharged capacitor (Q=0).  to put it another way, we will look at how much work one has to do to charge a capacitor.  That is also the energy stored in a capacitor. We will discuss the possibility of viewing that energy as being in the electric field. The idea that electric fields can contain energy plays a central role in the picture  and understanding we have of light and other forms of electromagnetic waves.