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JIPMER Jipmer Medical Solved Paper-2010

  • question_answer
    An electric current passes through a long straight copper wire. At a distance 5 cm from the straight wire, the magnetic field is B. The magnetic field at 20 cm from the straight wire would be

    A)  \[\frac{B}{6}\]            

    B)                         \[\frac{B}{4}\] 

    C)  \[\frac{B}{3}\]                                     

    D)                         \[\frac{B}{2}\]

    Correct Answer: B

    Solution :

    The magnetic field at a distance r from the straight wire \[B=\frac{{{\mu }_{0}}i}{2\pi r}\]  or \[B\propto \frac{1}{r}\] or \[\frac{{{B}_{2}}}{{{B}_{1}}}=\frac{{{r}_{1}}}{{{r}_{2}}}\] \[\therefore \]  \[\frac{{{B}_{2}}}{B}=\frac{5}{20}=\frac{1}{4}\] or \[{{B}_{2}}=\frac{B}{4}\]


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