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A metallic wire is folded to form a squa...

A metallic wire is folded to form a square loop a side `'a'`. It carries a current `'I'` and is kept perpendicular to a uniform magnetic field. If the shape of the loop is changed from square to a circle without changing the length of thw wire and current, the amount of work done in doing so is

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Verified by Experts

W = Find P.E - intial P.E
`W = -M_(f) B - (M_(i) B) , W = iB (A_i = A_f)`
` W = iB a^2 [ 1-4/pi]`
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