Question

We have an isolated conducting spherical shell of radius $10cm$. Some positive charge is given to it so that resulting electric field has a maximum intensity of $1.8\times {10}^{6}N{C}^{-1}.$ The same amount of negative charge is given to another isolated conducting spherical shell of radius $20cm$. Now, first shell is placed inside the second so that both are concentric as shown in the figure.

The electric potential at any point inside the first shell is

• A. $18\times {10}^{4}V$
• B. $9\times {10}^{4}V$
• C. $4.5\times {10}^{4}V$
• D. $1.8\times {10}^{4}V$

Answer 1

The correct option is B $9\times {10}^{4}V$

Let $q$ be the charge given to shell of radius $10cm$. So, the charge given to shell of radius $20cm$ will be $-q$
We know that the maximum electric field intensity is at the surface of shell
$⟹1.8\times {10}^{6}N{C}^{-1}=\frac{kq}{(0.1{)}^2}$
$⟹kq=1.8\times {10}^{4}N{m}^2{C}^{-1}$
Now the potential inside the smaller shell will be


$V=\frac{kq}{0.1}-\frac{kq}{0.2}$
$\therefore V=9\times {10}^{4}V$