# Average electric field over a spherical surface

#### alexmahone

Problem Statement
Show that the average electric field over a spherical surface, due to charges outside the sphere, is the same as the field at the center.
Relevant Equations
This is where I'm stuck.
I'm sure the average is going to be an integral, but $\displaystyle\frac{1}{4\pi R^2}\oint\mathbf{E}\cdot d\mathbf{a}$ gives me a scalar, not a vector.

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