Answer :
Answer:
894 electrons
Explanation:
The electrostatic force between the two charges is given by:
[tex]F=\frac{k q_1 q_2}{r^2}[/tex]
where we have
[tex]F=4.57\cdot 10^{-21} N[/tex] is the force
k is the Coulomb's constant
q1 = q2 =q is the magnitude of the charge on each sphere
r = 20.0 cm = 0.20 m is the distance between the two spheres
Substituting and solving for q, we find the charge on each sphere:
[tex]q=\sqrt{\frac{Fr^2}{k}}=\sqrt{\frac{(4.57\cdot 10^{-21} N)(0.20 m)^2}{9\cdot 10^9 Nm^2C^{-2}}}=1.43\cdot 10^{-16} C[/tex]
And since each electron has a charge of
[tex]e=1.6\cdot 10^{-19}C[/tex]
the net charge on each sphere will be given by
[tex]q=Ne[/tex]
where N is the number of excess electrons; solving for N,
[tex]N=\frac{q}{e}=\frac{1.43\cdot 10^{-16}C}{1.6\cdot 10^{-19}C}=894[/tex]