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JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Kirchhoff's Law, Cells

  • question_answer
    When a resistance of 2 ohm is connected across the terminals of a cell, the current is 0.5 A. When the resistance is increased to 5 ohm, the current is 0.25 A. The e.m.f. of the cell is                                 [MP PET 1999, 2000; Pb. PMT 2002; MP PMT 2000]

    A)                    1.0 V

    B)                                      1.5 V

    C)                    2.0 V                                

    D)            2.5 V

    Correct Answer: B

    Solution :

               Since \[i\,=\left( \frac{E}{R+r} \right),\] we get \[0.5=\frac{E}{2+r}\]                     ......(i) \[0.25=\frac{E}{5+r}\]                   .....(ii) Dividing (i) by (ii), we get \[2=\frac{5+r}{2+r}\] Þ \[r=1\Omega \] \ \[0.5=\frac{E}{2+1}\] Þ \[E=1.5V\]


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