c
\({{\text{r}}_{\text{1}}}{\text{  =  20 cm, E  =  20 cm}}{\text{., }}{{\text{r}}_{\text{2}}}{\text{  =  3 cm}}\)

હવે \({{\text{E}}_{\text{1}}}\,\, = \,\,\frac{{kQ}}{{r_1^2}}\) અને \({E_2}\,\, = \,\,\frac{{kQ{r_2}}}{{{R^3}}}\) તેથી \(\frac{{{E_2}}}{{{E_1}}}\,\, = \,\,\frac{{{r_2}.r_1^2}}{{{R^3}}}\)

\({E_2}\,\, = \,\,\frac{{3\,\, \times \,\,20\,\, \times \,\,20}}{{10\,\, \times \,\,10\,\, \times \,\,10}}\,\, \times \,\,100\,\, = \,\,120\,V/m\)