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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 25

  • question_answer
    An ammeter A of finite resistance, and a resistor R are joined in series to an ideal cell C. A potentiometer P is joined in parallel to R. The ammeter reading is \[{{I}_{0}}\] and the potentiometer reading is \[{{V}_{0}}\]. P is now replaced by a voltmeter of finite resistance. The ammeter reading now is \[I\]and the voltmeter reading is V.

    A) \[I>{{I}_{0}},\,\,V<{{V}_{0}}\]          

    B) \[I>{{I}_{0}},\,\,V={{V}_{0}}\]

    C) \[I={{I}_{0}},\,\,V<{{V}_{0}}\]

    D)        \[I<{{I}_{0}},\,\,V={{V}_{0}}\]

    Correct Answer: A

    Solution :

    [a] On connecting voltmeter, equivalent resistance of the circuit decreases. Therefore, current in circuit increases \[(I>{{I}_{0}})\]. \[\therefore \] Potential drop across ammeter + Potential drop across R = E.M.F. of cell. In second case due to increase in current through ammeter, potential drop across ammeter increases. Hence potential drop across R decreases.


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