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JEE Main 202126 AugustEvening Shift
Exam
JEE Main
Year
2021
Date
26 August
Shift
Evening Shift
Subject
Physics
Chapter
Capacitance

JEE Main 2021 · 26 August · Evening Shift · Physics · Capacitance

A parallel-plate capacitor with plate area A has separation d...

A parallel-plate capacitor with plate area AA has separation dd between the plates. Two dielectric slabs of dielectric constant K1{K}_{1} and K2{K}_{2} of same area A2\dfrac{A}{2} and thickness d2\dfrac{d}{2} are inserted in the space between the plates. The capacitance of the capacitor will be given by :

A parallel-plate capacitor with plate area A has separation d between the plates. Two dielectric slabs of dielectric

Options

  1. Aε0Ad(12+K1K2K1+K2)\dfrac{{ε}_{0}A}{d}\left(\dfrac{1}{2} + \dfrac{{K}_{1}{K}_{2}}{{K}_{1} + {K}_{2}}\right)
  2. Bε0Ad(12+2(K1+K2)K1K2)\dfrac{{ε}_{0}A}{d}\left(\dfrac{1}{2} + \dfrac{2\left({K}_{1} + {K}_{2}\right)}{{K}_{1}{K}_{2}}\right)
  3. Cε0Ad(12+K1+K2K1K2)\dfrac{{ε}_{0}A}{d}\left(\dfrac{1}{2} + \dfrac{{K}_{1} + {K}_{2}}{{K}_{1}{K}_{2}}\right)
  4. Dε0Ad(12+K1K22(K1+K2))\dfrac{{ε}_{0}A}{d}\left(\dfrac{1}{2} + \dfrac{{K}_{1}{K}_{2}}{2\left({K}_{1} + {K}_{2}\right)}\right)

Correct answer

A. ε0Ad(12+K1K2K1+K2)\dfrac{{ε}_{0}A}{d}\left(\dfrac{1}{2} + \dfrac{{K}_{1}{K}_{2}}{{K}_{1} + {K}_{2}}\right)

Step-by-step solution

A parallel-plate capacitor with plate area A has separation d between the plates. Two dielectric slabs of dielectric

Ceq=C1+C2C3C2+C3{C}_{eq} = {C}_{1} + \dfrac{{C}_{2}{C}_{3}}{{C}_{2} + {C}_{3}}

Ceq=Aε02d+K1Aε0d×K2Aε0dK1Aε0d+K2Aε0d{C}_{eq} = \dfrac{A{ε}_{0}}{2d} + \dfrac{\dfrac{{K}_{1}A{ε}_{0}}{d} \times \dfrac{{K}_{2}A{ε}_{0}}{d}}{\dfrac{{K}_{1}A{ε}_{0}}{d} + \dfrac{{K}_{2}A{ε}_{0}}{d}}

Ceq=Aε02d+Aε0d(K1K2K1+K2)=Aε0d(12+K1K2K1+K2){C}_{eq} = \dfrac{A{ε}_{0}}{2d} + \dfrac{A{ε}_{0}}{d}\left(\dfrac{{K}_{1}{K}_{2}}{{K}_{1} + {K}_{2}}\right) = \dfrac{A{ε}_{0}}{d}\left(\dfrac{1}{2} + \dfrac{{K}_{1}{K}_{2}}{{K}_{1} + {K}_{2}}\right)

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