Question

The ink drops have a mass m = 1.00×10⁻¹¹ kg each and leave the nozzle and travel horizontally toward the paper at velocity v = 16.0 m/s . The drops pass through a charging unit that gives each drop a positive charge q by causing it to lose some electrons. The drops then pass between parallel deflecting plates of length D0 = 1.60 cm , where there is a uniform vertical electric field with magnitude E = 7.80×10⁴ N/C

If a drop is to be deflected a distance d = 0.350 mm by the time it reaches the end of the deflection plate, what magnitude of charge q must be given to the drop? Assume that the density of the ink drop is 1000 kg/m3 , and ignore the effects of gravity.

Answer 1

To solve this problem we have to first calulate the time taken by drop to travel through the parallel deflecting plate

time taken by the drop to travel parallel deflecting plate is

Now Force due to Electric field on a charged particle "q" is given by

and we know that

and we have kinetics equation

From equation we have

So the charge given to the drop should be 8.974 *10^{-14} F