Electrostatics 5 Question 28

30. A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials having dielectric constants K1,K2 and K3 as shown. If a single dielectric material is to be used to have the same capacitance C in this capacitor then its dielectric constant K is given by

(2000,2M)

(a) 1K=1K1+1K2+12K3

(b) 1K=1K1+K2+12K3

(c) 1K=K1K2K1+K2+2K3

(d) K=K1K3K1+K3+K2K3K2+K3

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Answer:

Correct Answer: 30. (d)

Solution:

  1. Applying C=ε0Adt1t2+t1K1+t2K2, we have

ε0(A/2)dd/2d/2+d/2K1+d/2K3

+ε0(A/2)dd/2d/2+d/2K2+d/2K3=Kε0Ad

Solving this equation, we get

K=K1K3K1+K3+K2K3K2+K3



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