Capacitors

JEE Main level, numerical answer, medium

100 of 180

Question 100 of 180

A parallel plate capacitor has plate area 100m2100{m}^{2} and plate separation of 10m.10m. The space between the plates is filled up to a thickness 5m5m with a material of dielectric constant of 10.10. The resultant capacitance of the system is xpF.xpF. The value of ϵ0=8.85×10−12Fm−1{\epsilon }_{0}=8.85\times {10}^{-12}F{m}^{-1}. The value of xx to the nearest integer is ______.

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Answer: 161


Here, Plate area
A=100m2A=100{m}^{2}
Using, Capacity of parallel plate capacitor is,

C=kϵ0AdC=\dfrac{k{\epsilon }_{0}A}{d}; where dd is separation between the plates and kk is dielectric constant.
The capacitance with dielectric will be,

C1=10ϵ0(100)5{C}_{1}=\dfrac{10{ϵ}_{0}(100)}{5}
=200ϵ0=200{ϵ}_{0}
The capacitance without dielectric or air will be,

C2=ϵ0(100)5=20ϵ0{C}_{2}=\dfrac{{ϵ}_{0}(100)}{5}=20{ϵ}_{0}
{C}_{1}&{C}_{2} are in series so,
Ceqv.=C1C2C1+C2{C}_{\text{eqv.}}=\dfrac{{C}_{1}{C}_{2}}{{C}_{1}+{C}_{2}}
=4000ϵ0220=\dfrac{4000{ϵ}_{0}}{220}
=160.9×10−12≃161pF=160.9\times {10}^{-12}≃161pF

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