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 Fig. 2.3. This arrangement can be thought as a dielectric slab of thickness d (= d1+d2) and effective dielectric constant k. The k is


Since, the two dielectrics are connected in series, we can regard them as two capacitors in a series combination with different dielectrics.

For capacitor 1






For capacitor 2






Series equivalent




Also



On comparing the above two equations, we get


1