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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2009

  • question_answer
      The magnetic flux linked with a coil at any instant t is given by \[\phi =5{{t}^{3}}\,-100t+300,\] the emf induced in the coil after t = 2 s is

    A)  - 40 V                   

    B)         40 V

    C)  140 V                   

    D)         300 V

    Correct Answer: B

    Solution :

    Given, magnetic flux\[(\phi )=5{{t}^{3}}-100t+300\] \[\therefore \]  \[\frac{d\phi }{dt}=15{{t}^{2}}-100\] Induced emf\[e=-\frac{d\phi }{dt}\]                            \[=-(15{{t}^{2}}-100)\] After\[t\text{ }=2s.\]                         \[e=-(15\times {{2}^{2}}-100)\]                            \[=-(60-100)\]                            \[=40\,\,V\]


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