Question

Two small iron particles, each of mass $280mg$ , are placed at a distance $10cm$ apart. If $0.01\%$ of the electrons of one particle are transferred to the other, find the electric force between them. Atomic weight of iron is $56gmo{l}^{-1}$ and there are $26$ electrons in each atom of iron.

Answer 1

The Avogadro’s number is $6.022\times {10}^{23}$

So in $280mg$the number of atoms are $\frac{6.022\times {10}^{23}\times 280\times {10}^{-3}}{56}=3\times {10}^{27}$

The total number of electron in $3\times {10}^{27}$atoms will be $3\times 10^{27}\times 26e$

The charge transferred is $\frac{1}{100}\times 78\times 10^{27}e$ are transferred to the other atom placed at distance of $10cm$ the force will be

$F=k{\frac{Q_1\times Q_2}{r^2}}^{}$

$F=\frac{-1.40\times {10}^{26}}{0.01}$

$F=-1.40\times {10}^{28}$