Question

A copper sphere of 2 gm has $2\times {10}^{22}$ atoms. the charge on the nucleus of each atom is $29e$. How many fractions of electrons be eliminated to provide a charge of $2\mu C$ to the sphere?

Answer 1

Charge on each nucleus$=29eC$

∴ Net charge on nucleus of the sphere of mass $2$ gm

$=\left(29e\right)\times (2\times {10}^{22}C)$

$=(5.8\times {10}^{23})eC$

∴ Total number of electron on sphere

$=(5.8\times {10}^{23})$

[∵ Sphere is initially uncharged]

∴ Number of electrons in charge of $2\times {10}^{-6}C$

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

∴ Fraction of electrons, which is to be removed

$=\frac{1.25\times {10}^{13}}{5.8\times {10}^{23}}$

$=2.15\times {10}^{-11}$