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A thin circular wire carrying a current I has a magnetic moment M. The shape of the wire is changed to a square and it carries the same current. It will have a magnetic moment

 

  • Option 1)

    M

     

  • Option 2)

    \frac{4}{\pi^{2}M}

     

  • Option 3)

    \frac{4}{\pi M}

     

  • Option 4)

    \frac{\pi}{4M}

 

Answers (1)

best_answer

 

Magnetic moment (M) -

M=NiA

- wherein

N-number of turns in the coil 

i-current throughout the coil 

A-area of the coil 

 

Initial M=I.\pi r^{2}

Final M'=I.A'

      2\pi r=4L\ \Rightarrow L=\frac{\pi r}{2}

      A'=L^{2}=\frac{\pi^{2}r^{2}}{4}

        \frac{M'}{M}=\frac{I.\frac{\pi^{2}r^{2}}{4}}{I.\pi r^{2}}=\frac{\pi}{4}

\Rightarrow M'=\frac{\pi}{4}M

 

 

 


Option 1)

M

 

incorrect

Option 2)

\frac{4}{\pi^{2}M}

 

incorrect

Option 3)

\frac{4}{\pi M}

 

incorrect

Option 4)

\frac{\pi}{4M}

correct

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Plabita

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