Question

How many electron should be added or removed from a natural body of mass 10 milli gram so that it may remain hanging in air in an electric field of strength 100N/C directed upward . (g=10m/s²)

Answer 1

In equilibrium F=qE =mgq=mg/E=(10×10^-3×10)/100q=0.001 CSince q=ne n=q/e =.001/1.6×10^-19 = 6.25 × 10^15