Physics · Moving Charges and Magnetic Field

JEE Main 2025 — 3 April, Evening Shift — Question 46

A magnetic dipole experiences a torque of $80 \sqrt{3} \mathrm{~N} \mathrm{~m}$ when placed in uniform magnetic field in such a way that dipole moment makes angle of $60^{\circ}$ with magnetic field. The potential energy of the dipole is :

Option A:
$-80 J$
Correct
Option B:
$-40 \sqrt{3} \mathrm{~J}$
Option C:
$-60 J$
Option D:
$80 J$

Answer: A

Step-by-step solution

$\tau=M B \sin \theta$

$v=-M B \cos \theta$

$\frac{v}{\tau}=-\cot \theta$

$v=-80 \sqrt{3} \times \frac{1}{\sqrt{3}}=-80$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 3 April, Evening Shift
Subject: Physics
Chapter: Moving Charges and Magnetic Field
Topic: Force and Torque on Wires and Loops, Magnetic Dipole Moment

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Step-by-step solution

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