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

  • question_answer
      A rectangular loop carrying a current is placed in a uniform magnetic field B. The area enclosed by the loop is A. If there are n turns in the loop, the torque acting on the loop is given by:

    A) \[ni(\overrightarrow{A}\times \overrightarrow{B})\]            

    B) \[ni(\overrightarrow{A}\cdot \overrightarrow{B})\]

    C) \[\frac{i(\overrightarrow{A}\times \overrightarrow{B})}{n}\]                       

    D) \[\frac{i(\overrightarrow{A}\cdot \overrightarrow{B})}{n}\]

    Correct Answer: A

    Solution :

    (a) \[ni(\overrightarrow{A}\times \overrightarrow{B})\]                         \[\overrightarrow{\tau }=\overrightarrow{M}\times \overrightarrow{B}\]                         \[=ni(\overrightarrow{A}\times \overrightarrow{B})\]           \[(\because \,\overrightarrow{M}=ni\,\overrightarrow{A})\]


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