CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    A varying magnetic flux linking a coil is given by\[\phi -X{{t}^{2}}\]. If at time\[t=3\text{ }s,\]the emf induced is 9 V, then the value of\[X\]is:

    A)  \[0.66\text{ }Wb\text{ }{{s}^{-2}}\]    

    B)         \[1.5\text{ }Wb\text{ }{{s}^{-2}}\]

    C)  \[-\text{ }0.66\text{ }Wb\text{ }{{s}^{-2}}\]  

    D)         \[-1.5\text{ }Wb\text{ }{{s}^{-2}}\]

    E)  \[-\,0.33\,Wb{{s}^{-2}}\]

    Correct Answer: B

    Solution :

    From Faradays law, induced emf is \[e=-\frac{d\phi }{dt}\] Given,        \[\phi =X{{t}^{2}}\] \[\therefore \]  \[e=\frac{-d(X{{t}^{2}})}{dt}=-2t\,X\] Given,       \[t=3,\text{ }e=9\text{ }V\] \[\therefore \] \[X=\frac{9}{3\times 2}=1.5\,Wb\,{{s}^{-2}}\]


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