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CMC Medical CMC-Medical VELLORE Solved Paper-2009

  • question_answer
    The sheave of a galvanometer of resistance 100\[\Omega \] contains 25 divisions. It gives a deflection of one division on passing a current of \[4\times {{10}^{-4}}\text{A}\]. The resistance in ohm to be added to it, so that it may become a voltmeter of range 2.5 V is

    A)  150                                       

    B)  170

    C)  110                                       

    D)  220

    Correct Answer: A

    Solution :

                     The deflection of one division of galvanometer is given by the current \[=4\times {{10}^{-4}}A\] or the current sensitivity of galvanometer is \[=4\times {{10}^{-4}}A/div\] \[\therefore \]  \[{{i}_{g}}=\] full scale deflection = current sensitivity x total number of turns \[=4\times {{10}^{-4}}\times 25={{10}^{-2}}A\] Resistance of galvanometer\[=100\,\Omega \] The value of resistance required, \[R=\frac{V}{{{i}_{g}}}-G=\frac{2.5}{{{10}^{-2}}}-100\] \[=250-100=150\,\Omega \]


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