[问答题]
A parallel-plate capacu e()ysli7 3kmitord daf*hrpv7do- w3w(fl* 8h5x has fixed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.
