Electrostatics

JEE Main level, single correct, medium

164 of 311

Question 164 of 311

The electrostatic potential on the surface of uniformly charged spherical shell of radius R=10 cm\mathrm{R}=10 \mathrm{~cm} is 120 V. The potential at the centre of shell, at a distance r=5 cm\mathrm{r}=5 \mathrm{~cm} from centre, and at a distance r=15 cm\mathrm{r}=15 \mathrm{~cm} from the centre of the shell respectively, are :

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Answer: (A) 120 V,120 V,80 V120 \mathrm{~V}, 120 \mathrm{~V}, 80 \mathrm{~V}

Potential inside shell is equal to potential on surface
Vin=Vsurface =kQR=120 V\mathrm{V}_{\mathrm{in}}=\mathrm{V}_{\text {surface }}=\frac{\mathrm{kQ}}{\mathrm{R}}=120 \mathrm{~V}
at r=15 cm\mathrm{r}=15 \mathrm{~cm}
V=kQr=120×1015=80 V\mathrm{V}=\frac{\mathrm{kQ}}{\mathrm{r}}=\frac{120 \times 10}{15}=80 \mathrm{~V}

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