JEE Main 2014 · 6 Apr · Shift 1 · Physics Q17

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PhysicsSingle correct+4 / -1Question 17 of 90

A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is $3\times10^4$ V/m, the charge density of the positive plate will be close to :

6\times10^{-7}

C/m

^2

3\times10^{-7}

C/m

^2

3\times10^{4}

C/m

^2

6\times10^{4}

C/m

^2

Answer and worked solution

Official answer: A

The free charge density on the plate is
$\sigma=K\epsilon_0E=2.2\times8.85\times10^{-12}\times3\times10^4\approx5.8\times10^{-7}\approx6\times10^{-7}\text{ C/m}^2.$

Topics:Dielectrics Capacitors and capacitance

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JEE Main 2014 · 6 Apr · Shift 1, Physics question 17