# Floating electrons

An electron floats at rest above a sheet of charge with uniform charge density $$\sigma$$. What is $$\sigma$$ in $$\mbox{C/m}^2$$?

Details and assumptions

• The mass of the electron is $$9.1 \times 10^{-31}~\mbox{kg}$$.
• The electric charge on the electron is $$-1.6 \times 10^{-19}~\mbox{C}$$.
• The acceleration due to gravity is $$-9.8~\mbox{m/s}^2$$.
• The vacuum permittivity is $$\epsilon_0=8.85 \times 10^{-12}~\mbox{F/m}$$.
• If your answer is $$\num{1.23e-4}$$ submit 1.23E-4.
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