Question

How many electrons should be removed from a coin
of mas 1.6 g, so that it may float in an electric
field of intensity 109 N/C directed upward?
(1) 9.8 × 107
(2) 9.8 x 105
(3) 9.8 x 103
(4) 9.8 x 101
​

Answer 1

Answer:

E = 109

so, F=eE = 1.6x10^-19 x 109 = 174.4 x 10^-19 N

mg = 1.6 x 10 = 16 N

for floating,

16 - n x mass of electron x g = 174.4 x 10 ^10-19

so,

(16 - 174.4 x 10^-19)/9.1 x 10^-31 x 10= n

1.76 x 10^30 - 1587.05 x 10^11 = n