Question

An Oil drop has $6.39\times {10}^{-19}$ C change. Find out the number of electrons in this oil drop.

Answer 1

Charge on oil drop$=6.39\times {10}^{-19}C$
$\because 1.602\times {10}^{-19}C$ is charge on one electron.
$\because 6.39\times {10}^{-19}C$ is charge on $=\frac{6.39\times {10}^{-19}}{1.602\times {10}^{-19}}=4$ electrons.
The number of electrons in this oil drop is 4.