Question

A parallel plate capacitor of a
capacitance 100pF is to be constructed
by using paper sheets of 1mm thickness
as dielectric. If the dielectric
constant of paper is 4, the
number of circular metal foils
of diameter 2cm each required
for the purpose is,​

Answer 1

The answer will be 10

Explanation:

According to the problem the capacitance of the parallel plate is 100 pF

The thickness of the sheets is given as 1 mm

The dielectric constant of the paper is given

Now let the number of foils required is p and it will need (p-1) capacitors

Now let the dielectric constant is k

Therefore the capacitance is given by

c = ke0(p-1)A/d

=> (p-1) = cd/ke0A = cd/k x 4πe0A = 4π/πr^2 =  4cd/ k x 4πe0r^2

                 = 4 x 10^(-1) x 1 x 10^(-3) x 9 x 10^9/4(1.0 x 10^(-2))^2 = 9

p = 10