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JEE Main & Advanced Sample Paper JEE Main Sample Paper-23

  • question_answer
    Two parallel rails of a railway track insulated from each other and with the ground are connected to a milli voltmeter. The distance between the rails is 1 m. A train is travelling with a velocity of 72 \[km-{{h}^{-1}}\] along the track. The reading of the milli voltmeter (in mV) is (vertical component of the earth's magnetic induction is \[2\times {{10}^{-5}}T\])

    A)  \[1.44\]                                    

    B)  \[0.72\]

    C)  \[0.4\]                                      

    D)  \[0.2\]

    Correct Answer: C

    Solution :

    Induced emf, \[e=Bvl\] V = velocity of train \[=72\times \frac{5}{18}\,=20\,m{{s}^{-1}}\] \[e=2\times {{10}^{-5}}\,\times 20\,\times 1=2\,\times {{10}^{-5}}\,\times 20\] \[=40\times {{10}^{-5}}\,V=40\,\times {{10}^{-2}}\,mV=0.4\,mV\]


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