Question

How many excess electrons must be added to an isolated spherical conductor 26.0 cm in diameter to produce an electric field of magnitude 1250 N/C just outside the surface?

Answer 1

Electric field just outside the surface of spherical conductor is given by,

E = k*Q/R^2

here, k = 9*10^9

E = 1250 N/C

R = radius = diameter/2 = 26.0/2 cm = 0.13 m

So, charge(Q) = E*R^2/k = 1250*0.13^2/(9*10^9)

Q = 2.35*10^-9 C

now, Q = n*e

So, number of electron = n = Q/e = (2.35*10^-9)/(1.60*10^-19)

n = 1.47*10^10

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