A parallel plate capacitor has plates of area A separated by distance d between them. It is filled with a…


A parallel plate capacitor has plates of area A separated by distance d between them. It is filled with a dielectric which has a dielectric constant that varies as Kx=K01+αx where x is the distance measured from one of the plates. If αd<<1, the total capacitance of the system is best given by the expression:
  1. AK0ε0d1+αd2
  2. AK0ε0d1+αd22
  3. AK0ε0d1+α2d22
  4. AK0ε0d1+αd

Solution

Capacitance of element, dC=K01+αxε0Adx
1dC=0ddxK0ε0A1+αx
1C=1K0ε0Aαln1+αd
Given αd1
1C=1K0ε0Aααd-α2d22
1C=dK0ε0A1-αd2
C=K0ε0Ad1+αd2

Asked in: JEE Main 2020 (07 Jan Shift 1)

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