A charged oil drop is suspended in a uniform field of 3 × 104V/m so that it neither falls nor rises. The charge on the drop will be (take the mass of the charge = 9.9 × 10–15kg and g = 10m/s2 )
(a) 3.3 × 10 –18C
(b) 3.2 × 10 –18C
(c) 1.6 × 10 –18C
(d) 4.8 × 10 –18C.
