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

  • question_answer
    A rectangular coil of 100 turns and size \[0.1\text{ }m\times 0.05\text{ }m\] is placed perpendicular to a magnetic field of 0.1 T. If the field drops to 0.05 T in 0.05 second, the magnitude of the e.m.f. induced in the coil is:

    A) 2 V                 

    B)             3V           

    C) 0.5 V                           

    D)             6 V                            

    Correct Answer: C

    Solution :

    (c) 0.5 V Here, area of coil \[A=0.1\text{ }m\times 0.05\text{ }m=5\times {{10}^{-3}}{{m}^{2}}\] Number of turns, \[N=100\] Initial flux linked with the coil \[{{\phi }_{1}}=BA\,\cos \,\theta =0.1\times 5\times {{10}^{-3}}\cos \,0{}^\circ =5\times {{10}^{-4}}Wb\] Final flux linked with the coil \[{{\phi }_{2}}=0.05\times 5\times {{10}^{-3}}\cos 0{}^\circ =25\times {{10}^{-5}}Wb\] \[=2.5\times {{10}^{-4}}Wb\] The magnitude of induced emf in the coil is \[\varepsilon =\frac{N|\Delta \,\phi |}{\Delta t}=\frac{N|{{\phi }_{2}}-{{\phi }_{1}}|}{t}\] \[=\frac{100|2.5\times {{10}^{-4}}-5\times {{10}^{-4}}|}{0.05}\]             \[=\frac{100\times 2.5\times {{10}^{-4}}}{0.05}V=0.5\,V\]


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