Question

The dielectric strength in air is $3\times {10}^{6}V{m}^{-1}$. Charge to be given to a conducting sphere of radius 2m is :

• A. $1.33\times {10}^{-3}C$
• B. $2.66\times {10}^{-3}C$
• C. $3\times {10}^{-3}C$
• D. infinite

Answer 1

The correct option is A $1.33\times {10}^{-3}C$

Considering that the charge is Q. The dielectric strength of air is given. The maximum charge which can be given without ionising the air around it is given by,
$E=kQ/r^2$
$3\times {10}^6=9\times {10}^9\times Q/4$
$Q=1.33\times {10}^{-3}C$