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

  • question_answer
    A positive charge 'q' of mass 'm' is moving along the + x axis. We wish to apply a uniform magnetic field B for time \[\Delta t\]so that the charge reverses its direction crossing the y axis at a distance d. Then:       [JEE ONLINE 12-04-2014]

    A) \[B=\frac{mv}{qd}\]and\[\Delta t=\frac{\pi d}{v}\]

    B) \[B=\frac{mv}{2qd}\]and\[\Delta t=\frac{\pi d}{2v}\]

    C) \[B=\frac{2mv}{qd}\]and\[\Delta t=\frac{\pi d}{2v}\]

    D) \[B=\frac{2mv}{qd}\]and\[\Delta t=\frac{\pi d}{v}\]

    Correct Answer: C

    Solution :

    [c] The applied magnetic field provides the required centripetal force to the charge particle, so it can move in circular path of radius\[\frac{d}{2}\]
    \[\therefore \]\[Bqv=\frac{m{{v}^{2}}}{d/2}\]or\[B=\frac{2mv}{qd}\]
    Time interval for which a uniform magnetic field is applied\[\Delta t=\frac{\pi .\frac{d}{2}}{v}\](particle reverses its direction after time \[\Delta t\]by covering semi-circle). \[\Delta t=\frac{\pi d}{2v}\]


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