RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    From resistances of 100 ohm each are connected in the form of a square. The  effective resistance along the diagonal points   P R. is:

    A)  \[100\,\Omega \]                           

    B)  \[180\,\Omega \]

    C)  \[220\,\Omega \]                           

    D)  \[440\,\Omega \]

    Correct Answer: A

    Solution :

    Here: Resistance of arm\[PQ({{R}_{1}})=100\,\Omega \] Resistance of arm\[PQ({{R}_{2}})=100\,\Omega \] Resistance of arm \[RS({{R}_{3}})=100\,\Omega \] Resistance of arm\[SP({{R}_{4}})=100\,\Omega \] Resistance of upper arm \[{{R}_{1}}\] and \[{{R}_{2}}\] are connected in series. Hence, their resultant resistance Similarly the resistance of lower half\[{{R}_{3}}\] and\[{{R}_{4}}\] are also connected in series. Hence, their resultant resistance is \[{{R}_{L}}={{R}_{3}}+{{R}_{4}}=100+100=200\,\Omega \] So, equivalent resistance   \[\frac{1}{{{R}_{PR}}}=\frac{1}{{{R}_{U}}}+\frac{1}{{{R}_{L}}}\]          \[=\frac{1}{200}+\frac{1}{200}=\frac{2}{200}=\frac{1}{100}\] So, \[{{R}_{PR}}=100\,\Omega \]


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