Two point charges -4 and 4, constituting an electric dipole, are placed at (-9, 0, 0) cm and (9, 0, 0) cm in a uniform electric field of strength 10⁴ NC⁻¹. The work done on the dipole in rotating it from the equilibrium through 180° is: (a) 18.4 mJ (b) 12.4 mJ (c) 16.4 mJ (d) 14.4 mJ

Answer: (d). p = q(2l) = 4×10⁻⁶ × 0.18 = 7.2×10⁻⁷ C m From equilibrium through 180°: W = pE(cos 0° - cos 180°) = 2pE W = 2 × 7.2×10⁻⁷ × 10⁴ = 14.4×10⁻³ J So the answer is (d) 14.4 mJ.

Two point charges -4 and 4, constituting an electric dipole, are… | JEE Main 2025 (23 Jan, Shift 2)

Q21JEE Main 2025 · 23 JAN · SHIFT 2Easy

Electric Dipole

Two point charges $-4\,\mu\text{C}$ and $4\,\mu\text{C}$ , constituting an electric dipole, are placed at $(-9, 0, 0)\text{ cm}$ and $(9, 0, 0)\text{ cm}$ in a uniform electric field of strength $10^{4}\text{ NC}^{-1}$ . The work done on the dipole in rotating it from the equilibrium through $180^\circ$ is:

Show answer and solution

Answer: (d)

$p = q(2l) = 4\times10^{-6} \times 0.18 = 7.2\times10^{-7}$ C m
From equilibrium through $180^\circ$ : $W = pE(\cos 0^\circ - \cos 180^\circ) = 2pE$
$W = 2 \times 7.2\times10^{-7} \times 10^{4} = 14.4\times10^{-3}$ J
So the answer is (d) 14.4 mJ.

Report a mistake

Electric Dipole question from JEE Main 2025 (23 Jan, Shift 2)

More questions on Electric Dipole