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Question: Answered & Verified by Expert

A wire carrying current I is tied between points P and Q and is in the shape of a circular arc of radius R due to a uniform magnetic field B (perpendicular to the plane of the paper, as shown in the figure) in the vicinity of the wire. If the wire subtends an angle 2θo at the center of the circle (of which it forms an arch) then the tension in the wire is:

PhysicsMagnetic Effects of CurrentJEE MainJEE Main 2015 (11 Apr Online)
Options:
  • A IBR
  • B IBRsinθ0
  • C IBR2sinθ0
  • D IBRθ0sinθ0
Solution:
2028 Upvotes Verified Answer
The correct answer is: IBR


Consider any small element dl of arc of angle dθ . Then magnetic force dF=Idl.B outwards  



For equilibrium of element 

Idl B=2T sin2

For small angle sinθθ

IdlB=2Tdθ2

Idl B=TdlR

T=IBR

 

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