InterviewSolution
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InterviewSolution
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A wire of length l is bent in the form a circular coil of some turns. A current I flows through the coil. The coil is placed in a uniform magnetic field B. The maximum torqur on the coil can beA. `(iBl^(2))/(4pi)`B. `(iBl^(2))/(pi)`C. `(iBl^(2))/(2pi)`D. `(2iBl^(2))/(pi)` |
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Answer» Correct Answer - A Let `N` be the number turns and `R` the redius of the coil. Then, `l=2piRN` or `R=l/(2piN) …(i)` Now magnetic moment of the coil is `M=NiA=Ni(piR^(2))` `=(Nipi)(l/(4pi^(2)N^(2)))=(il^(2))/(4piN)` Maximum value of `M` can be `M_(max)=(il^(2))/(4pi) at N=1` `:. tau_(max)=M_(max)B sin 90^(@)=(iBl^(2))/(4pi)`. |
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