NTSE Sample Paper NTSE SAT Practice Test-17

  • question_answer
    How many times will the total resistance of n identical conductors be reduced if the series  arrangement is changed to parallel one?

    A) \[{{n}^{2}}\]                          

    B) \[\frac{1}{{{n}^{2}}}\]

    C) \[\frac{1}{{{n}^{3}}}\]                       

    D) \[{{n}^{3}}\]

    Correct Answer: B

    Solution :

    [b] Let R be the resistance of each of the n conductors. Effective resistance in series combination, \[{{R}_{s}}=R+R+....+n\,\,\,times\] Effective resistance in parallel combination, \[\frac{1}{{{R}^{p}}}=\frac{1}{R}+\frac{1}{R}+.....+n\]   times \[=\frac{n}{R}\] or \[{{R}_{p}}=\frac{R}{n}\] \[\therefore \frac{{{R}_{p}}}{{{R}_{s}}}=\frac{R}{\frac{n}{nR}}\] \[=\frac{1}{{{n}^{2}}}\]


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