12th Class Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव Question Bank Case Based (MCQs) - Moving Charges and Magnetism

  • question_answer
    An electron having momentum \[2\,.\,4\times {{10}^{-23}}\,kg\] enters a region of uniform magnetic field of \[0\,.\,15\,T\]. The field vector makes an angle of \[30{}^\circ \]with the initial velocity vector of the electron. The radius of the helical path of the electron in the field shall be

    A) 2 mm

    B) 1 mm

    C) \[\frac{\sqrt{3}}{2}mm\]

    D) \[0\,.\,5\,mm\]

    Correct Answer: D

    Solution :

    This radius of the helical path of the electron in the uniform magnetic field is \[r=\frac{m{{v}_{\bot }}}{eB}=\frac{mv\sin \theta }{eB}\] \[=\frac{\left( 2.4\times {{10}^{-23}}\,kg\,m/s \right)\times \sin \,30{}^\circ }{\left( 1.6\times {{10}^{-19}}C \right)\times 0\,.\,15T}\] \[=5\times {{10}^{-4}}m=0\,.\,5\times {{10}^{-3}}m=0.5\,mm\]


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