- Home
- Standard 12
- Physics
1. Electric Charges and Fields
hard
At a point $20\, cm$ from the centre of a uniformly charged dielectric sphere of radius $10\, cm$, the electric field is $100\, V/m$. The electric field at $3\, cm$ from the centre of the sphere will be.......$V/m$
A
$150$
B
$125$
C
$120$
D
$0$
Solution
(c) Electric field outside of the sphere ${E_{out}} = \frac{{kQ}}{{{r^2}}}$ $…(i)$
Electric field inside the dielectric sphere ${E_{in}} = \frac{{kQx}}{{{R^3}}}$$…(ii)$
From $(i)$ and $(ii)$, ${E_{in}} = {E_{out}} \times \frac{{{r^2}x}}{R}$
$==>$ At $3\, cm$, $E = 100 \times \frac{{3\,{{(20)}^2}}}{{{{10}^3}}} = 120\,V/m$
Standard 12
Physics