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An electric dipole consists of two unlike charges of magnitude \(2 \times 10^{-6}\) C each and separated by 4 cm. The dipole is placed in an external electric field of \(10^5\) N/C. Calculate the work done by an external agent to turn the dipole thro…

Q.8 An electric dipole consists of two unlike charges of magnitude \(2 \times 10^{-6}\) C each and separated by 4 cm. The dipole is placed in an external electric field of \(10^5\) N/C. Calculate the work done by an external agent to turn the dipole through 180º.

Doubtly Asked Board exam · March 2026 hsc 12th Save WhatsApp Report
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Answer: \(W = 0.016\) J

Dipole moment \(p = q(2l) = 2\times10^{-6} \times 0.04 = 8\times10^{-8}\) C m.

Work done in rotating the dipole from \(\theta_1\) to \(\theta_2\): \(W = pE(\cos\theta_1 - \cos\theta_2)\). Taking the dipole initially in stable equilibrium (\(\theta_1 = 0^\circ\)) and turning it through 180° (\(\theta_2 = 180^\circ\)):

\[W = pE(\cos 0^\circ - \cos 180^\circ) = 2pE = 2 \times 8\times10^{-8} \times 10^5 = 1.6\times10^{-2}\ \text{J}\]
Doubtly AI · 27 Oct 2026 AI-verified · Oct 2026 Report
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