A charged sphere of radius R carrying total charge Q is enclosed by an imaginary concentric sphere of radius 2R. What is the total electric flux through the imaginary sphere?

Q/epsilon0
Q/(2*epsilon0)
4Q/epsilon0
2Q/epsilon0

Correct answer: Q/epsilon0

Solution

By Gauss's law the net electric flux through any closed surface equals (charge enclosed)/epsilon0. The imaginary sphere of radius 2R encloses the entire charge Q of the inner sphere, so the flux is Q/epsilon0, independent of the radius 2R.

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