What I didn't understand but now think I do is that the potential energy is negative when you start with the top plate and then goes to zero as you reach the bottom plate with the coordinates chosen.
It's not the positive or negative sign that doesn't make sense. The complimentary value of the potential is given. If you measure from the bottom, you are giving a different value for the potential energy than when you measure from the top which is the distance potential the electron can...
Why is the electric potential of an electron in a capacitor measured from the negative plate and not the positive plate here?
This is from Liboff Introductory quantum mechanics 1st(current is 4th) edition:
I don't understand why the distance z is measured from the bottom plate if the...