JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Different Measuring Instruments

  • question_answer
    The length of a wire of a potentiometer is 100 cm, and the emf of its standard cell is E volt.  It is employed to measure the e.m.f of a battery whose internal resistance is 0.5 W.  If the balance point is obtained at l = 30 cm from the positive end, the e.m.f. of the battery is                              [AIEEE 2003]

    A)         \[\frac{30E}{100}\]

    B)         \[\frac{30E}{100.5}\]

    C)         \[\frac{30E}{(100-0.5)}\]

    D)         \[\frac{30(E-0.5i)}{100}\], where i is the current in the potentiometer

    Correct Answer: A

    Solution :

                                             From the principle of potentiometer \[V\propto l\]        Þ \[\frac{V}{E}=\frac{l}{L}\]; where V = emf of battery, E = emf of standard cell, L = Length of potentiometer wire         \[V=\frac{El}{L}=\frac{30E}{100}\].


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