NEET Sample Paper NEET Sample Test Paper-48

  • question_answer
    Circular loop bf a wire and a long straight wire carry current \[{{\operatorname{I}}_{c}} and {{I}_{e}}\]respectively as shown in figure. Assuming that these are placed in the same plane. The magnetic field will be zero at the centre of the loop when the separation H is:

    A) \[\frac{{{I}_{e}}R}{{{I}_{c}}\pi }\]                              

    B) \[\frac{{{I}_{\operatorname{c}}}R}{{{I}_{\operatorname{e}}}\pi }\]     

    C) \[\frac{\pi {{I}_{\operatorname{c}}}}{{{I}_{\operatorname{e}}}R}\]                  

    D) \[\frac{{{I}_{\operatorname{c}}}\pi }{{{I}_{\operatorname{e}}}R}\]

    Correct Answer: A

    Solution :

    Magnetic field due to closed loop of radius       R \[{{\vec{B}}_{1}}=\frac{{{\mu }_{\operatorname{o}}}{{\operatorname{I}}_{c}}}{2\operatorname{R}}~~\odot  Out of the plane\] Magnetic field due to straight wire carrying currently \[{{\vec{B}}_{2}}=\frac{{{\mu }_{\operatorname{o}}}{{\operatorname{I}}_{c}}}{2\pi \operatorname{H}}~~\otimes \operatorname{Into} the plane\] It is given that \[{{\vec{B}}_{net}}\]at loop centre is zero \[{{\vec{B}}_{1}}-{{\vec{B}}_{2}} =0\] \[{{\vec{B}}_{1}}={{\vec{B}}_{2}}\] \[\frac{{{\mu }_{\operatorname{o}}}{{\operatorname{I}}_{c}}}{2\operatorname{R}}=\frac{{{\mu }_{\operatorname{o}}}{{\operatorname{I}}_{c}}}{2\pi \operatorname{H}}\] \[\operatorname{H}=\frac{\operatorname{R}{{\operatorname{I}}_{c}}}{\pi {{\operatorname{I}}_{c}}}\]


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