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If ∮ₛ ⃗E· d⃗S=0 over a surface, then

Asked in NEET 2023 · Gauss's law and enclosed charge

• (1) The number of flux lines entering the surface must be equal to the number of flux lines leaving it
• (2) The magnitude of electric field on the surface is constant
• (3) All the charges must necessarily be inside the surface
• (4) The electric field inside the surface is necessarily uniform

Step-by-step solution

Why the other options are wrong

• (2) Zero net flux says nothing about the size of the field at each point; a dipole's field through a surface enclosing neither charge varies from place to place.
• (3) Zero flux means the net enclosed charge is zero: the charges may all be outside, or equal and opposite ones may be inside.
• (4) The field inside can be anything; zero net flux constrains only the total outward flux.

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