Question

Two identical spheres carrying charges $-9\mu C$ and 5$\mu C$ respectively are kept in contact and then separated from each other. Point out true statement from the following. In first sphere

• A. $1.25\times {10}^{13}$ electrons are in deficit
• B. $1.25\times {10}^{13}$ electrons are in excess
• C. $2.15\times {10}^{13}$ electrons are in excess
• D. $2.15\times {10}^{13}$ electrons are in deficit

Answer 1

The correct option is B $1.25\times {10}^{13}$ electrons are in excess

After initial contact and separation, each sphere will have charge,

$q=\frac{-9\mu C+5\mu C}{2}=-2\mu C$

The number of electron,

$n=\frac{-2\times {10}^{-6}}{-1.6\times {10}^{-19}}=1.25\times {10}^{13}$ electron

$1.25\times {10}^{13}$ electron as in excess in each sphere.

The correct option is B.