A parallel plate capacitor is made of two circular plates separated by a distance $5\ mm$ and with a dielectric of dielectric constant $2.2$ between them. When the electric field in the dielectric is $3 \times 10^4$ $ Vm^{-1}$ the charge density of the positive plate will be close to
JEE MAIN 2014, Medium
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Electric field in presence of dielectric between the two plates of a parallel plate capacitor is given by,
$E=\frac{\sigma}{K \varepsilon_{0}}$
Then, charge density
${\sigma=K \varepsilon_{0} E}$
${=2.2 \times 8.85 \times 10^{-12} \times 3 \times 10^{4} \approx 6 \times 10^{-7} \,\mathrm{C} / \mathrm{m}^{2}}$
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