An oil drop of the radius 2 mm with a density 3 g cm - 3 is held stationary under a constant electric field 3 . 55 × 10 5 V m - 1 in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess? consider g = 9 . 81 m s - 2 .

Step-by-step solution

q E = M g ⇒ n e E = ρ 4 3 π r 3 × g ⇒ n × 1 . 6 × 10 - 19 × 3 . 55 × 10 5 = 3 × 10 3 × 4 3 × π × 2 × 10 - 3 3 × 9 . 81 ⇒ n = 173 × 10 ( 3 - 9 - 5 + 19 ) ⇒ n = 1 . 73 × 10 10 .