Physics - Electrostatics Question with Solution | TestHub

Given,

Number of electrons$\left(n\right)=4\times {10}^{10}$${\mathrm{ m}}^{-3}$

Diameter of sphere$\left(D\right)=20 \mathrm{c}\mathrm{m}$

Radius of sphere$\left(r\right)=\frac{20}{2}=10 cm=0.01 \mathrm{m}$

According to equation,

$E_{\mathrm{o}\mathrm{u}\mathrm{t}\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}}=\frac{q}{4\pi {\epsilon }_0{r}^2}$

$=\frac{ne}{4\pi {\epsilon }_0{r}^2}$

Here,$r=20\times {10}^{-2}\mathrm{m}$

$=\frac{4\times {10}^{10}\times 1.6\times {10}^{-19}\times 9\times {10}^9}{{\left(20\times {10}^{-2}\right)}^2}$

$=\frac{4\times 1.6\times 9}{20\times 20\times {10}^{-4}}$

$=\frac{4\times 1.6\times 9\times {10}^4}{20\times 20}$

$=1.6\times 9\times {10}^2$

$=1.44\times {10}^3=1440 N{\mathrm{C}}^{-1}$