KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    Two sources of emf 6V and internal resistance \[3\,\Omega \] and \[2\Omega \] are connected to an external resistance R as shown. If potential difference across battery A is zero then value of R is -

    A) \[1\Omega \]                 

    B) \[2\Omega \] 

    C) \[3\Omega \]                             

    D) \[4\Omega \]

    Correct Answer: A

    Solution :

    Current in the circuit is i and \[i=\frac{{{\in }_{eq}}}{R+{{r}_{eq}}}\]
    \[{{\in }_{eq}}=6+6=12,\] \[{{r}_{eq}}=3+2=5\]
    p.d. across A=0 
    \[{{\in }_{A}}-i{{r}_{A}}=0,\] where \[{{\in }_{A}}=6V\] and \[{{r}_{A}}=3\Omega \]
    \[6-\frac{12}{R+5}\times 3=0\]\[R=1\Omega \]   

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