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JEE Main 2014 · Dielectrics

Dielectrics question from JEE Main 2014

Q104JEE Main 2014Medium

Dielectrics

A parallel plate capacitor is made of two circular plates separated by a distance 5 mm5\text{ mm} and with a dielectric of dielectric constant 2.22.2 between them. When the electric field in the dielectric is 3×104 V/m3 \times 10^{4}\text{ V/m} the charge density of the positive plate will be close to:

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Answer: (a)

  1. Field in dielectric E=σKϵ0⇒σ=Kϵ0EE=\frac{\sigma}{K\epsilon_0} \Rightarrow \sigma=K\epsilon_0E.
  2. σ=2.2×8.85×10−12×3×104≈5.8×10−7 C/m2\sigma=2.2\times8.85\times10^{-12}\times3\times10^4\approx5.8\times10^{-7}\text{ C/m}^2
  3. So the answer is (a) 6×10−7 C/m26\times10^{-7}\text{ C/m}^2.
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