NEET Sample Paper NEET Sample Test Paper-19

  • question_answer A charged particles a uniform magnetic field with velocity vector making an angle of \[30{}^\circ \] with the magnetic field. The particle describes a helical trajectory of pitch \[x.\]The radius of the helix is

    A) \[\frac{x}{2\pi }\]                               

    B) \[\frac{x}{2\sqrt{2}\pi }\]

    C) \[\frac{x}{2\sqrt{3}\pi }\]                  

    D) \[\frac{\sqrt{3}x}{2\pi }\]  

    Correct Answer: C

    Solution :

    Pitch\[X=\frac{2\pi m\upsilon \cos {{30}^{o}}}{qB}=\frac{2\pi m\upsilon }{qB}.\frac{\sqrt{3}}{2}\](1) Radius \[r=\frac{m\upsilon \sin {{60}^{o}}}{qB}=\frac{m\upsilon }{2qB}\]                  (2) From Eqs. (1) and (2), we get \[r=\frac{x}{2\sqrt{3}\pi },\]which is choice [c]. Hence, the correction option is [c].


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