Question

A parallel plate capacitor is made of two circular plates separated by a distance of $5mm$ and with a dielectric of dielectric constant $2.2$ between them. When the electric field in the dielectric field in the dielectric is $3\times {10}^{4}V/m$, the charge density of the positive plate will be close to :

• A. $6\times {10}^{-7}C/m^2$
• B. $3\times {10}^{-7}C/m^2$
• C. $3\times {10}^{4}C/m^2$
• D. $6\times {10}^{4}C/m^2$

Answer 1

The correct option is B $3\times {10}^{-7}C/m^2$

$\sigma =\frac{q}{4\pi R^2}$

$=\frac{3\times {10}^{+14}}{4\pi \times {(5\times {10}^{-3})}^2}$

$=3\times {10}^{-7}$