Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): When some charges lie inside a closed surface and some lie outside it, the electric field at points on the surface is due to all these charges.
Reason (R): The total electric flux through a closed surface is \(q/\varepsilon_0\), where \(q\) is the total charge enclosed by the surface.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
Assertion (A) When some charges lie inside a closed surface and some lie outside it, the electric field at points on the surface is due to all these charges. — True. The field at any point comes from every charge, by Coulomb’s law and the superposition principle. A charge outside the surface also adds to the field on it.
Reason (R) The total electric flux through a closed surface is \(q/\varepsilon_0\), where \(q\) is the total charge enclosed by the surface. — True. This is Gauss’s law.
Why Reason (R) does not explain Assertion (A)?
R is about the total flux through the surface. Only the enclosed charge decides this total.
A is about the field at each point of the surface. That field depends on the charges outside as well, even though their net flux through the closed surface is zero.
NCERT (2026-27):
Gauss’s Law – “We state Gauss’s law without proof: Electric flux through a closed surface S = q/ε0 … q = total charge enclosed by S.”
Gauss’s Law – “(iii) In the situation when the surface is so chosen that there are some charges inside and some outside, the electric field … is due to all the charges, both inside and outside S. The term q on the right side of Gauss’s law, however, represents only the total charge inside S.”