JEE Main & Advanced Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव JEE PYQ-Magnetic Effects Of Current

  • question_answer
    The dipole moment of a circular loop carrying a current I, is m and the magnetic field at the centre of the loop is \[{{B}_{1}}\]. When the dipole moment is doubled by keeping the current constant, the magnetic field at the centre of the loop is \[{{B}_{2}}.\] The ratio \[\frac{{{B}_{1}}}{{{B}_{2}}}\] is: [JEE Main Online 08-04-2018]

    A) \[\sqrt{2}\]

    B) \[\frac{1}{\sqrt{2}}\] 

    C) 2

    D) \[\sqrt{3}\]

    Correct Answer: A

    Solution :

    [a] \[I(\pi {{r}^{2}})=M,2M=I\pi {{(r')}^{2}}\]
                                        \[r'=\sqrt{2}r\]
    \[{{B}_{1}}=\frac{{{\mu }_{o}}I}{2r}\]
    \[{{B}_{2}}=\frac{{{\mu }_{o}}I}{2\sqrt{2}r}\]
    \[\therefore \frac{{{B}_{1}}}{{{B}_{2}}}=\frac{\sqrt{2}}{1}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner