Two related questions (from Electromagnetics by Notaros)
The dielectric of a parallel-plate capacitor has two homogeneous parts, referred to
as dielectric 1 and dielectric 2. The boundary surface between the parts is flat and
parallel to the capacitor plates. The dielectric strength of dielectric 1 is twice that
of dielectric 2. If a voltage larger than the breakdown voltage of the capacitor is
applied across the capacitor terminals, the breakdown occurs in
(A) dielectric 1.
(B) dielectric 2.
(C) both dielectrics simultaneously.
(D) Need more information.
and the second one:
Repeat the previous question but assuming that the boundary surface between
the two material parts constituting the dielectric of the parallel-plate capacitor is
perpendicular to the capacitor plates.
The Attempt at a Solution
In the first case, the thought the D field would be same in both dielectrics, because of the boundary conditions. Therefore, the dielectric with the smaller ε would reach breakdown first. In the second, the E fields are the same (tangential E field is equal across dielectric boundaries) and so the two would breakdown simultaneously (same E and same voltage).
However, the solution manual gives the first answer to be D) and the second to be B)
Does anyone know why this would be?