Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : If an electric dipole of dipole moment 30 × 10⁻⁵ C m is enclosed by a closed surface, the net flux coming out of the surface will be zero.
Reason R : Electric dipole consists of two equal and opposite charges.
In the light of above, statements, choose the correct answer from the options given below.

Solution

Physics sir · 4 steps

Gauss's law only cares about net charge inside, and a dipole's net charge is +q - q = 0.

1. Gauss's law. The total flux out of any closed surface depends only on the net charge enclosed: φ = q_(enc)/ε₀. Charges outside, or how the enclosed charges are arranged, do not matter.
2. Charge inside. A dipole is a charge +q and a charge -q a small distance apart. So the net enclosed charge is +q + (-q) = 0, whatever the dipole moment is.

   φ = ((+q) + (-q))/ε₀ = 0

3. Check A and R. A is true: the net flux is zero. R is true, and it is exactly the fact that makes the enclosed charge zero. The value 30 × 10⁻⁵ C m is only there to distract you.
4. So. Both statements are true and R correctly explains A, which is option (d).

The idea to keep. For flux through a closed surface, first find the net enclosed charge. Field lines may leave and re-enter, but only q_(enc) decides the total.

Answer from the NTA final answer key. Solution by PrepWiser.