Question

If the electric potential at a certain distance from a point charge is $900V$ and electric intensity is $225V{m}^{-1}$ . The charge is :

• A. $4\times {10}^{-7}C$
• B. $2\times {10}^{-7}C$
• C. $4\times {10}^{-3}C$
• D. $2\times {10}^{-5}C$

Answer 1

The correct option is A $4\times {10}^{-7}C$

we know $v=\frac{kq}{r}$
and $E=\frac{kq}{r^2}$
$\Rightarrow 900=\frac{k.q}{r}and225=\frac{kq}{r^2}$
solve the above equation

$\Rightarrow 225=\frac{kq\times 900\times 900}{kq\times kq}$

$\Rightarrow q=\frac{9\times 9\times {10}^4}{225\times 9\times {10}^9}$

$\Rightarrow q=4\times {10}^{-7}C.$