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NEET Sample Paper NEET Sample Test Paper-5

  • question_answer
    A particle of mass m and charge q moves with a constant velocity V along the positive x-direction. It enters a region containing a uniform magnetic field B directed along the negative z-direction, extending from X = a to X = b. The minimum value of V required, so that the particular can just enter the region \[X>b\] is:

    A)  \[\frac{qbB}{m}\]                             

    B)  \[\frac{q(b-a)B}{m}\]

    C)  \[\frac{qa\,B}{m}\]               

    D)  \[\frac{q\,(b+a)}{2m}\]

    Correct Answer: B

    Solution :

    As      \[\frac{m{{V}^{2}}}{r}=qVB\]     or \[V=\frac{qB}{m}\,(r)\] \[\therefore \] \[{{V}_{\min }}=\frac{qB}{m}({{r}_{\min }})=\frac{qB}{m}(b-a)\]        Note that r should be \[(b-a)\] to go just outside of field rigid.


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