JIPMER Jipmer Medical Solved Paper-2004

  • question_answer
    A circular coil of mean radius of 7 cm and having 4000 turns is rotated at the rate of 1800 revolutions per minute in the earths magnetic field (B = 0.5 gauss), the emf induced in coil will be :

    A)  1.158 V       

    B)                                        0.58 V                  

    C)         0.29 V                                  

    D)         5.8 V

    Correct Answer: B

    Solution :

    Here: \[n=4000,\]\[B=0.5\times {{10}^{-4}}Wb\text{/}{{m}^{2}}\] Rate of rotation of coil \[=1800\,\,\text{rev/}\min \] \[=\frac{1800}{60}=30\,\text{rev/}\sec \] \[\omega =2\pi f=2\pi \times 30=60\pi \,rad\text{/}s,\] \[r=7\,cm=0.07\,m\] Now area of coil \[A=\pi {{r}^{2}}=\pi \times {{(0.07)}^{2}}=49\pi \times {{10}^{-4}}{{m}^{2}}\] Now the maximum energy induced is \[e=BA\,n\omega \]    \[=0.5\times {{10}^{-4}}\times 49\pi \times {{10}^{-4}}\times 4000\times 60\pi \]    \[=0.58\,V\]


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