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BCECE Medical BCECE Medical Solved Papers-2015

  • question_answer
    When a battery of emf 8 V with internal resistance \[0.5\,\,\Omega \] is charged by a 120 V DC supply using a series resistance of \[15.5\,\,\Omega \], then the terminal voltage of the battery is

    A)  11.5 V  

    B)  20 V   

    C)  21.5 V  

    D)  12,3 V

    Correct Answer: A

    Solution :

    Here, emf of battery = 8V Internal resistance of the battery, \[r=0.5\,\Omega \] Voltage of D.C. supply = 120 V External resistance, \[R=15.5\,\Omega \]. When the battery of emf 8 V is charged from a DC supply of 120 V, the effective emf in the circuit is                 \[\varepsilon -120-8=112\,V\] Total resistance of the circuit \[=R+r\]                 \[=(15.5+0.5)\,\,\Omega =16\,\,\Omega \] \[\therefore \] Current in the circuit during charging                 \[I=\frac{\varepsilon }{R+r}=\frac{112}{16}=7A\] \[\therefore \] Terminal voltage of the battery, V = emf of the battery + voltage drop across the battery \[=8+Ir=8+7\,(0.5)=11.5\,V\]


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