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12th Class Physics Magnetism Question Bank MCQ - Moving Charges and Magnetism

  • question_answer
    Two particles A and B with same charges and different masses (\[{{m}_{A}}\] and \[{{m}_{B}}\] respectively) are moving in a plane inside uniform magnetic field which is perpendicular to the plane. The speed of the particles are \[{{v}_{A}}\] and \[{{v}_{B}}\] respectively and the trajectories are as shown in figure. Then:

    A) \[{{m}_{A}}{{v}_{A}}<{{m}_{B}}{{v}_{B}}\]         

    B) \[{{m}_{A}}{{v}_{A}}>{{m}_{B}}{{v}_{B}}\]

    C) \[{{m}_{A}}<{{m}_{B}}\] and \[{{v}_{A}}<{{v}_{B}}\]

    D) \[{{m}_{A}}={{m}_{B}}\] and \[{{v}_{A}}<{{v}_{B}}\]

    Correct Answer: B

    Solution :

    (b) \[{{m}_{A}}{{v}_{A}}>{{m}_{B}}{{v}_{B}}\] Radius of circular path,             \[{{r}_{a}}=\frac{{{m}_{A}}{{v}_{A}}}{qB}\] and \[{{r}_{B}}=\frac{{{m}_{B}}{{v}_{B}}}{qB}\] According to question, \[{{r}_{A}}<{{r}_{B}}\] \[\therefore \frac{{{m}_{A}}{{v}_{A}}}{qB}>\frac{{{m}_{B}}{{v}_{B}}}{qB}\] or \[{{m}_{A}}{{v}_{A}}>{{m}_{B}}{{v}_{B}}\]


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