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JEE Main 20198 AprilMorning Shift
Exam
JEE Main
Year
2019
Date
8 April
Shift
Morning Shift
Subject
Physics
Chapter
Capacitance

JEE Main 2019 · 8 April · Morning Shift · Physics · Capacitance

Voltage rating of a parallel plate capacitor is 500V . Its...

Voltage rating of a parallel plate capacitor is 500V.500V . Its dielectric can withstand a maximum electric field of 106V/m.{10}^{6}V / m . The plate area is 10−4m2{10}^{- 4}{m}^{2} . What is the dielectric constant if the capacitance is 15pF15pF ?
(givenϵ0=8.86×10−12C2/Nm2)\left(given{ϵ}_{0} = 8.86 \times {10}^{- 12}{C}^{2} / N{m}^{2}\right)

Options

  1. A3.83.8
  2. B8.58.5
  3. C4.54.5
  4. D6.26.2

Correct answer

B. 8.58.5

Step-by-step solution

Electric field inside capacitor =Vd= \dfrac{V}{d}
=VdAkε0Akε0=VCAkε0= \dfrac{V}{d}\dfrac{Ak{ε}_{0}}{Ak{ε}_{0}} = \dfrac{VC}{Ak{ε}_{0}}\left(∵ \dfrac{kA{ε}_{0}}{d} = C\right)<br/><br/>{10}^{6} = \dfrac{500 \times 15 \times {10}^{- 12}}{{10}^{- 4} \times k \times 8.85 \times {10}^{- 12}}<br/><br/>k = \dfrac{15 \times 500}{8.85 \times {10}^{- 4} \times {10}^{6}} = \dfrac{75}{8.85}<br/><br/>k = 8.47 \approx 8.5
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