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Question: Answered & Verified by Expert
A parallel plate capacitor has the space between its plates filled by two slabs of thickness \( \frac{d}{2} \) each and dielectric constant \( K_{1} \) and \( K_{2} . d \) is the plate separation of the capacitor. The capacity of the capacitor is :
PhysicsCapacitanceJEE Main
Options:
  • A \( \frac{2 \varepsilon_{0} d}{A}\left(\frac{K_{1}+K_{2}}{K_{1} K_{2}}\right) \)
  • B \( \frac{2 \varepsilon_{0} A}{d}\left(\frac{K_{1} K_{2}}{K_{1}+K_{2}}\right) \)
  • C \( \frac{2 \varepsilon_{0} A}{A}\left(K_{1}+K_{2}\right) \)
  • D \( \frac{2 \varepsilon_{0} A}{d}\left(\frac{K_{1}+K_{2}}{K_{1} K_{2}}\right) \)
Solution:
1816 Upvotes Verified Answer
The correct answer is: \( \frac{2 \varepsilon_{0} A}{d}\left(\frac{K_{1} K_{2}}{K_{1}+K_{2}}\right) \)
Let us understand this such that two capacitors are connected in series with K1 and K2 as dielectric constant of the dielectric mediums present in between the plates.
See the figure down below for better understanding.

C1=K1ε0A(d2)=2K1ε0Ad
C2=K2ε0A(d2)=2K2ε0Ad
Now since both C1 and C2 are arranged in series, we apply the formula for series combination of capacitor:
1Cs=1C1 +1C2=d2K1ε0A+d2K2ε0A
=d2ε0AK1+K2K1K2
Cs=2ε0AdK1K2K1+K2

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