MGIMS WARDHA MGIMS WARDHA Solved Paper-2008

  • question_answer
    In the Wheat stone's network given, \[P=10\Omega ,\]\[Q=20\Omega ,R=15\Omega ,\]\[S=30\Omega ,\]the current passing through the battery (of negligible internal resistance) is

    A) 0.36 A                                   

    B) zero

    C) 0.ISA                                     

    D) 0.72 A

    Correct Answer: A

    Solution :

    The balanced condition for Wheatstone's bridge is \[\frac{P}{Q}=\frac{R}{S}\] as is obvious from the given values. No, current flows through galvanometer is zero. Now, P and R are in series, so resistance \[{{R}_{1}}=P+R\] \[=10+15=25\,\Omega \] Similarly, Q and S are in series, so resistance \[{{R}_{2}}=Q+S\] \[=20+30=50\,\Omega \] Net resistance of the network as\[{{R}_{1}}\]and\[{{R}_{2}}\]are in parallel \[\frac{1}{R}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}\] \[\therefore \]  \[R=\frac{25\times 50}{25+50}=\frac{50}{3}\Omega \] Hence,     \[I=\frac{V}{R}=\frac{6}{\frac{50}{3}}=0.36A\]


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