AIIMS AIIMS Solved Paper-2000

  • question_answer
    What should be amount of current through the ring of radius of 5 cm so that field at the centre is equal to the earths magnetic field \[=eV\] is?

    A) 0.28 A                   

    B)        5.57 A   

    C)        2.8 A                     

    D)        None of these

    Correct Answer: B

    Solution :

                    Magnetic field at the centre of coil of radius a carrying current i is \[F=\frac{G{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}\] \[{{m}_{1}}{{m}_{2}}\]  \[\therefore \] Given, \[{{F}_{1}}={{F}_{2}}\] \[\frac{G\left( \frac{M}{81} \right)M}{{{x}^{2}}}=\frac{GM\times M}{{{(60R-x)}^{2}}}\]   \[\Rightarrow \] \[\frac{1}{81{{x}^{2}}}=\frac{1}{{{(60R-x)}^{2}}}\]


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