I assigned a problem from the seventh edition of Sears, Zemansky, and Young
(problem 27-36) to my students without reading it carefully first. (I trust
I am not the only one to make this mistake occasionally!)
Now that I am working out the solution, I think I may have found an
inconsistency in the problem. Perhaps you can help me find the/my mistake.
"A parallel-plate capacitor consists of two horizontal conducting plates of
equal area A. The bottom plate is resting on a fixed support, and the top
plate is suspended by four springs of spring constant k, positioned at each
of the four corners of the top plate. The plates, when uncharged, are
separated by a distance zo. A battery connected to the plates produces a
potential difference V between them. This causes the plate separation to
decrease to z. Neglect fringing effects.
part b) Obtain an _expression_ that relates the plate separation