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JEE Main 20253 AprilEvening Shift
Exam
JEE Main
Year
2025
Date
3 April
Shift
Evening Shift
Subject
Physics
Chapter
Magnetic Effects of Current

JEE Main 2025 · 3 April · Evening Shift · Physics · Magnetic Effects of Current

A magnetic dipole experiences a torque of 80 3 ~N ~m when placed in...

A magnetic dipole experiences a torque of 803 N m80 \sqrt{3} \mathrm{~N} \mathrm{~m} when placed in uniform magnetic field in such a way that dipole moment makes angle of 60∘60^{\circ} with magnetic field. The potential energy of the dipole is :

Options

  1. A80 J80 \mathrm{~J}
  2. B−403 J-40 \sqrt{3} \mathrm{~J}
  3. C−60 J-60 \mathrm{~J}
  4. D−80 J-80 \mathrm{~J}

Correct answer

D. −80 J-80 \mathrm{~J}

Step-by-step solution

τ=M×\tau=\mathrm{M} \times\mathrm{B}=\mathrm{MB}sin⁡60=32MB=803\sin 60=\frac{\sqrt{3}}{2} \mathrm{MB}=80 \sqrt{3}
MB=160U=−M⋅B=−MBcos⁡60U=−160×1/2=−80 J\begin{aligned} & \mathrm{MB}=160 \\ & \mathrm{U}=-\mathrm{M} \cdot \mathrm{B}=-\mathrm{MB} \cos 60 \\ & \mathrm{U}=-160 \times 1 / 2=-80 \mathrm{~J}\end{aligned}
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