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## Homework Statement

Charge of uniform surface density (4.0 nC/m

^{2}) is distributed on a spherical surface (radius = 2.0 cm). What is the total electric flux through a concentric spherical surface with a radius of 4 cm?

## Homework Equations

[tex]\Phi = E 4 \pi r^2 = \frac{q}{\epsilon_0}[/tex]

[tex]E=k_e \frac{Q}{r^2}[/tex]

## The Attempt at a Solution

I tried finding the electric field due to the charge at the surface of the concentric spherical surface

[tex]E = (8.9 \times 10^9) \frac{(4 \times 10^{-9})}{(4 \times 10^{-2})^2} = 22250[/tex]

then used this to find the flux:

[tex]22250 \times 4 \times \pi \times (4 \times 10^{-2})^2 =447.36[/tex]

But what's wrong with my approach? This is very different from the correct answer (2.3 N.m

^{2}/C).