Question

The breakdown electric intensity for air is $3\times {10}^6$ V/m. The maximum charge that can be held by a sphere of radius $1mm$ is:

• A. $0.33C$
• B. $0.33nC$
• C. $3.3C$
• D. $3.3\mu C$

Answer 1

The correct option is B $0.33nC$

man electric field when $\nu$ change is
given occurs at the surface $\therefore eE=\frac{k\nu }{r^2}$
$\therefore$ for breakdown not to occur
$\frac{kq}{r^2}=3\times {10}^{-6}$
$\nu =\frac{3\times {10}^{-6}\times {10}^{-6}}{4\times {10}^4}$
$\nu =0.33\times {10}^{-9}c$
$\nu =0.33nc$