Find the capacitance of a capacitor if the area of its plates is S, the distance between the plates is `d_(0)` and a dielectric sheet of the thickness `dltd_(0)` is inserted into the capacitor (Fig. 25.4)

Explanation

The capacitance of a capacitor will remain unchanged, if we place a very thin piece of foil on top of the insulating layer. For this reason the capacitance sought should be regarded as made up of the capacitances of two capacitors connected in series, with capacitances
`C_(1)=(epsi epsi_(0)S)/(d) and C_(2)=(epsi_(0)S)/(d_(0)-d)` will remce of