Question Number 39792 by NECx last updated on 11/Jul/18
$${A}\:{positive}\:{charge}\:{of}\:{magnigude} \\ $$$$\mathrm{2}.\mathrm{5}\mu{C}\:{is}\:{at}\:{the}\:{centre}\:{of}\:{an}\:{uncharged} \\ $$$${spherical}\:{conducting}\:{shell}\:{of}\:{inner} \\ $$$${radius}\:\mathrm{60}{cm}\:{and}\:{an}\:{outer}\:{radius} \\ $$$${of}\:\mathrm{90}{cm}. \\ $$$$\left({i}\right){find}\:{the}\:{charge}\:{densities}\:{on}\:{thd} \\ $$$${inner}\:{and}\:{outer}\:{surfaces}\:{of}\:{the} \\ $$$${shell}\:{and}\:{the}\:{total}\:{charge}\:{on}\:{each} \\ $$$${surface}. \\ $$$$\left.{ii}\right){find}\:{the}\:{electricity}\:{field} \\ $$$${everywhere}. \\ $$
Commented by NECx last updated on 11/Jul/18
$${please}\:{help} \\ $$
Answered by tanmay.chaudhury50@gmail.com last updated on 11/Jul/18
$$\left.{i}\right){surface}\:{charge}\:{density}\:\left(\sigma\right)\:{on}\:{the}\:{inner} \\ $$$${surface}\:{shell}\:\sigma_{{i}} =\frac{−\mathrm{2}.\mathrm{5}×\mathrm{10}^{−\mathrm{6}} }{\mathrm{4}\Pi×\left(\mathrm{60}×\mathrm{10}^{−\mathrm{2}} \right)^{\mathrm{2}} } \\ $$$${surface}\:{charge}\:{density}\left(\sigma\right)\:{on}\:{the}\:{outer} \\ $$$${surface}\:{shell}\:\:\sigma_{{o}} =\frac{\mathrm{2}.\mathrm{5}×\mathrm{10}^{−\mathrm{6}} }{\mathrm{4}\Pi\left(\mathrm{90}×\mathrm{10}^{−\mathrm{2}} \right)^{\mathrm{2}} } \\ $$$${electric}\:{field}\:{inside}\:{the}\:{shell}\:{is}\:{zero}…{because} \\ $$$${charge}\:{at}\:{centre}\:{and}\:{induced}\:{charged}\:{on}\:\:{the} \\ $$$${inner}\:{wall}\:{of}\:{shell}\:{balance}\:{each}\:{other} \\ $$$${E}×\mathrm{4}\Pi{r}^{\mathrm{2}} =\frac{\mathrm{2}.\mathrm{5}\mu{C}+\left(−\mathrm{2}.\mathrm{5}\mu{C}\right)}{\epsilon_{\mathrm{0}} } \\ $$$${so}\:{E}=\mathrm{0} \\ $$$${for}\:{outside}\:{the}\:{shell}\:{wall}.. \\ $$$${E}×\mathrm{4}\Pi{R}^{\mathrm{2}} =\frac{\mathrm{2}.\mathrm{5}\mu{C}+\left(−\mathrm{2}.\mathrm{5}\mu{C}\right)+\left(\mathrm{2}.\mathrm{5}\mu{C}\right)}{\epsilon_{\mathrm{0}} } \\ $$$${E}=\frac{\mathrm{2}.\mathrm{5}×\mathrm{10}^{−\mathrm{6}} }{\mathrm{4}\Pi\epsilon_{\mathrm{0}} \left(\mathrm{90}×\mathrm{10}^{−\mathrm{2}} \right)^{\mathrm{2}} } \\ $$
Commented by NECx last updated on 11/Jul/18
$${This}\:{is}\:{cool}\:.\:{Thank}\:{you}\:{so}\:{much} \\ $$