12th Class Physics Electro Magnetic Induction Question Bank MCQ - Electromagnetic Induction

  • question_answer
    A square loop side 12 cm and resistance \[0.60\,\Omega \]. is placed vertically in the east-west plane. A uniform magnetic field of 0.10 T is set up across the plane in north-east direction. The magnetic field is decreased to zero in 0.6 s at a steady rate. The magnitude of current during this time interval is:

    A) \[1.42\times {{10}^{-3}}A\]                 

    B) \[2.67\times {{10}^{-3}}A\]

    C) \[3.41\times {{10}^{-3}}A\]         

    D) \[4.21\times {{10}^{-3}}A\]

    Correct Answer: B

    Solution :

    (b) \[2.67\times {{10}^{-3}}A\] Here, Area \[A={{l}^{2}}={{(12\,\,cm)}^{2}}=14\times {{10}^{-2}}{{m}^{2}}\] \[R=0.60\,\Omega ,\,{{B}_{1}}=0.10T,\,\theta =45{}^\circ ,\,{{B}_{2}}\] \[=0,\,dt=0.6\,s\] initial flux, \[{{\phi }_{1}}={{B}_{1}}A\,\cos \theta \] \[=0.10\times 14\times {{10}^{-2}}\times \cos \,45{}^\circ =9.9\times {{10}^{-4}}Wb\] Final flux, \[{{\phi }_{2}}=0\] Induced emf, \[\varepsilon =\frac{|d\phi |}{dt}=\frac{|{{\phi }_{2}}-{{\phi }_{1}}|}{dt}=\frac{|9.8\times {{10}^{-4}}|}{0.6\,s}\]             \[=1.65\times {{10}^{-3}}V\] Current, \[l=\frac{\varepsilon }{R}=\frac{165\times {{10}^{-3}}}{0.6}=2.75\times {{10}^{-3}}A\]


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