CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    A circular coil of 5 turns and of 10 cm mean diameter is connected to a voltage source. If the resistance of the coil is \[10\,\Omega \]the voltage of the source so as to nullify the horizontal component of earths magnetic field of 30 A turn\[{{m}^{-1}}\]at the centre of the coil should be

    A)  6 V, plane of the coil normal to magnetic meridian

    B)  2 V, plane of the coil normal to magnetic meridian

    C)  6 V, plane of the coil along the magnetic meridian

    D)  2 V, plane of the coil along the magnetic meridian

    E)  4V, plane of the coil normal to magnetic meridian

    Correct Answer: A

    Solution :

    Magnetic field of 1 A turn/m \[=4\pi \times {{10}^{-7}}T\] Field at centre \[B=\frac{{{\mu }_{0}}NI}{2r}=\frac{{{\mu }_{0}}N}{2r}\times \frac{V}{R}\] Or                           \[V=\frac{2rRB}{{{\mu }_{0}}N}\] \[\therefore \]\[B=\frac{2\times (5\times {{10}^{-2}})\times 10\times (30\times 4\pi \times {{10}^{-7}})}{(4\pi \times {{10}^{-7}})\times 5}\]   or        \[V=6\]volt To nullify the horizontal component of magnetic field of earth, plane of the coil should be normal to magnetic meridian.


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