NEET Sample Paper NEET Sample Test Paper-18

  • question_answer
    A square loop of side 1 m is placed in a perpendicular magnetic field. Half of the area of the loop lies inside the magnetic field. A battery of emf 10 V and negligible internal resistance is connected in the loop. The magnetic field changes with time according to the relation \[B=(0.01-2t)\]Tesla. The net emf in the circuit will be

    A)  1 V                             

    B)  11 V

    C)  9 V                             

    D)  10 V

    Correct Answer: C

    Solution :

    Let the net e.m.f.in the circuit be\[{{\varepsilon }_{net}}\] Now,\[{{\varepsilon }_{net}}={{\varepsilon }_{ind}}+{{\varepsilon }_{b}}\] Where \[{{\varepsilon }_{ind}}\]is the induced e.m. fand \[{{\varepsilon }_{b}},\]the e. m. f. of the battery. Applying Faraday's law \[{{\varepsilon }_{ind}}=-\frac{d\phi }{dt}\] If we make anticlockwise circumvention in the loop then the area vector is vertically upward and the magnetic field is vertically downward. Now, \[\phi =\vec{B}.\vec{A}=-BA\] \[\therefore \]    \[\phi =-(0.01-2t)\frac{1}{2}\Rightarrow \frac{d\phi }{dt}=1\,V\] So, \[{{\varepsilon }_{ind}}=-\frac{d\phi }{dt}=-1\,V\] \[\therefore \]\[{{\varepsilon }_{net}}={{\varepsilon }_{ind}}+{{\varepsilon }_{b}}=-1+10=9\,V\] Hence, the correction option is [c].


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