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Question: Answered & Verified by Expert

A wire loop carrying current i is placed in the x-y plane as shown in the figure. If an external uniform magnetic field B=Bi^ is switched on, then the torque acting on the loop is

PhysicsMagnetic Effects of CurrentJEE Main
Options:
  • A iBa2π3-34j^
  • B iBa23π-34j^
  • C iBa2π3-32j^
  • D iBa23π-32j^
Solution:
2046 Upvotes Verified Answer
The correct answer is: iBa2π3-34j^
∵   Magnetic dipole moment of current loop is M =I A

here area of loop A = Area of sector of circle - area of

13πa2-12a cos60°×a sin60°×2



A = π a 2 × 1 3 - 2 × 1 2 × a 2 3 2 a . = π a 2 3 - 3 4 a 2 , A = π 3 - 3 4 a 2 k ^

∵   torque on loop placed in uniform magnetic field is

τ = M × B = I A × B = I π 3 - 3 4 a 2 k ^ × B i ^ = IB a 2 π 3 - 3 4 j ^

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