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AMU Medical AMU Solved Paper-1995

  • question_answer
    A high voltage electrical cable consists of a steel core surrounded by six aluminium conductors. If the resistance of the steel core is\[{{R}_{s}}\]and that of the aluminuium conductors is \[{{R}_{a}},\]the resistance of the composite cable is

    A)  \[{{R}_{s}}+6{{R}_{a}}\]

    B)  \[\frac{1}{{{R}_{s}}}+\frac{1}{6{{R}_{a}}}\]

    C)  \[\frac{{{R}_{s}}{{R}_{a}}}{{{R}_{s}}+6{{R}_{a}}}\]

    D)  \[\frac{{{R}_{s}}{{R}_{a}}}{6{{R}_{s}}+{{R}_{a}}}\]

    Correct Answer: D

    Solution :

    : The resistances are in parallel \[\therefore \] \[\frac{1}{R}=\frac{1}{{{R}_{s}}}+\frac{1}{{{R}_{a}}}+\frac{1}{{{R}_{a}}}+\frac{1}{{{R}_{a}}}+\frac{1}{{{R}_{a}}}+\frac{1}{{{R}_{a}}}+\frac{1}{{{R}_{a}}}\] Or \[\frac{1}{R}=\frac{{{R}_{a}}+6{{R}_{s}}}{{{R}_{s}}{{R}_{a}}}\] or \[R=\frac{{{R}_{s}}{{R}_{a}}}{6{{R}_{s}}+{{R}_{a}}}\]


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