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AFMC AFMC Solved Paper-2010

  • question_answer
    Two wires of the same material but of different diameters carry the same current J. If the ratio of their diameters is 2 : 1, then the corresponding ratio of their mean drift velocities will be

    A)  4 : 1                                      

    B) 1 : 1

    C) 1 : 2                                       

    D) 1 : 4

    Correct Answer: D

    Solution :

    Drift velocity \[{{v}_{d}}=\frac{I}{nAe}=\frac{I\times 4}{n\pi {{D}^{2}}e}\] ie, \[{{v}_{d}}\propto \frac{1}{{{D}^{2}}}\] \[\frac{{{v}_{{{d}_{1}}}}}{{{v}_{{{d}_{2}}}}}=\frac{D_{2}^{2}}{D_{1}^{2}}={{\left( \frac{1}{2} \right)}^{2}}=\frac{1}{4}\]


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