Explain why there must always be some nonzero electric field outside the plates of a parallel-plate capacitor (Figure P26.13a), which means that the idealization shown in Figure P26.13b, with all the field lines confined to the region between the plates, can never be exact. (Consider the potential difference between the plates for paths outside the edges.)

Data from Figure P26.13

(a) (b) ++ +9 b.