The electric field of an electric dipole for large distances (r >> 2a, where 2a is the length of dipole) is proportional to
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → r−3
A dipole has zero net charge, so far away the fields of +q and −q almost cancel. What remains depends on the separation 2a relative to r. On the axis, for \( r \gg a \),
\( \displaystyle E = \frac{1}{4\pi\varepsilon_0}\,\frac{2p}{r^{3}} \)
and on the equatorial line \( E = \frac{1}{4\pi\varepsilon_0}\,\frac{p}{r^{3}} \). In every direction the field of a dipole falls as \( 1/r^{3} \).
Why the other options are incorrect
Option (1) r−1 — Incorrect. \( r^{-1} \) is how the potential of a point charge (or the field of a long line charge) varies.
Option (2) r−2 — Incorrect. \( r^{-2} \) is the field of a single point charge; for a dipole the two opposite charges cancel this leading term.
Option (3) r−3/2 — Incorrect. No standard charge distribution gives an \( r^{-3/2} \) field.
NCERT (2026-27):
The Field of an Electric Dipole – …
