# Two Spheres

Two spheres that are $$35\text{ cm}$$ apart have equal charge. How many excess electrons must be on each sphere if the magnitude of the force of repulsion between them is $$2.2\times10^{-21}\text{ N}$$?

• The charge of a single electron is $$e=1.6\times10^{-19}\text{ C}$$.
• For this problem, assume the electrostatic constant is $$k_e=8.988\times10^9\text{ N m}^2\text{ C}^{-2}$$.