In Milikan’s experiment, static electric charge on the oil drops has been obtained by shining X-rays. If the static electric charge on the oil drop is –1.282 × 10^–18C, calculate the number of electrons present on it.

Given:

Charge present on oil drop = –1.282 × 10^–18 C

Charge of one electron = 1.6× 10^-19 J

Charge on oil drop, = ne

Where

n = number of electrons

e = 1.6× 10^-19 J

n = [–1.282 × 10^–18 C] / [1.6× 10^-19]

n = 8 electrons

Therefore, the number of electrons present on oil drop is 8 electrons.