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For a given charge configuration enclosed (partly) by a spherical Gaussian surface, when the FLUX of the electric field through that spherical surface is being calculated, the electric field appearing in the flux integral is due to:

1. q2 (the enclosed charge only)
2. Only the positive charges
3. +q1 and -q1 only
4. All the charges

Correct answer: All the charges

Solution

In Gauss's law, the net flux equals q_enclosed/epsilon0 and depends only on the charge inside. However, the electric field vector E at any point on the Gaussian surface is the total field due to ALL charges - both inside and outside the surface. Contributions of external charges cancel out in the net flux integral, but they still contribute to E itself. Hence the field in the flux integrand is due to all the charges.

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