Question:
A parallel plate capacitor is made of two dielectric blocks in series. One of the blocks has thickness d1 and dielectric constant k1 and the other has thickness
d2 and dielectric constant k2 as shown in the figure. This arrangement can be thought of as a dielectric slab of thickness d = d1 + d2 and effective dielectric
constant k. The k is
(a) k1d1 + k2d2/d1+d2
(b) k1d1 + k2d2/k1 + k2
(c) k1k2 (d1 + d2)/(k1d1 + k2d2)
(d) 2k1k2/k1 + k2
Solution:
The correct answer is (c) k1k2 (d1 + d2)/(k1d1 + k2d2)