Given below are two statements:
Statement I: At large distances, the electric field of a dipole falls off as \(1/r^{2}\), like the field of a single charge.
Statement II: In a uniform electric field, an electric dipole feels a net force along the direction of the field.
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 Statement I and Statement II are incorrect
A dipole has charges \( +q \) and \( -q \) a small distance apart. Far away, their fields nearly cancel. So the dipole field is weaker than the field of one charge.
Statement I At large distances, the electric field of a dipole falls off as \(1/r^{2}\), like the field of a single charge. — False. Far from a dipole, \( E \) is proportional to \( p/r^{3} \). So it decreases as \( 1/r^{3} \). The field of a single charge decreases more slowly, as \( 1/r^{2} \).
Statement II In a uniform electric field, an electric dipole feels a net force along the direction of the field. — False. In a uniform field, the force on \( +q \) is \( q\vec E \) and the force on \( -q \) is \( -q\vec E \). These two forces are equal and opposite, so the net force is zero. The field only turns the dipole.
NCERT (2026-27):
The field of an electric dipole – “Notice the important point that the dipole field at large distances falls off not as 1/r2 but as 1/r3. …”
Dipole in a Uniform External Field – “There is a force qE on q and a force –qE on –q. The net force on the dipole is zero, since E is uniform. …”