JEE Main & Advanced Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव Question Bank Self Evaluation Test - Moving Charges and Mangetism

  • question_answer
    The magnetic field at O due to current in the infinite wire forming a loop as shown in Fig. is

    A) \[\frac{{{\mu }_{0}}I}{2\pi d}(\cos {{\phi }_{1}}+\cos {{\phi }_{2}})\]  

    B) \[\frac{{{\mu }_{0}}I2I}{4\pi d}(tan{{\theta }_{1}}+\tan {{\theta }_{2}})\]

    C) \[\frac{{{\mu }_{0}}I}{4\pi d}(sin{{\phi }_{1}}+\sin {{\phi }_{2}})\]

    D) \[\frac{{{\mu }_{0}}I}{4\pi d}(cos{{\theta }_{1}}+\sin {{\theta }_{2}})\]

    Correct Answer: A

    Solution :

    [a] Using \[B=\frac{{{\mu }_{0}}I}{4\pi d}\left[ \sin \,{{\theta }_{1}}+\sin \,{{\theta }_{2}} \right]\] But \[{{\theta }_{1}}+{{\phi }_{1}}={{90}^{o}}\]   or  \[{{\theta }_{1}}={{90}^{o}}-\phi \], \[\sin {{\theta }_{1}}=\sin ({{90}^{o}}-{{\phi }_{1}})=\cos {{\phi }_{1}}\] Similarly, \[\sin \,{{\theta }_{2}}=\cos \,{{\phi }_{2}}\] \[{{B}_{net}}=\frac{{{\mu }_{0}}I}{2\pi d}\left( \cos \,{{\phi }_{1}}+\cos \,{{\phi }_{2}} \right)\]


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