Punjab Medical Punjab - MET Solved Paper-2003

  • question_answer
    Two equal resistances \[R\] are joined with voltage source \[V\] in (i) series (h) parallel, the ratio of electrical power consumed in two cases will be:

    A) \[1:4\]                                  

    B) \[4:1\]

    C) \[2:1\]                                  

    D) \[2:1\]

    Correct Answer: A

    Solution :

    (i) In series : total resistance\[=R+R=2R\] Power consumed            \[{{P}_{1}}=\frac{{{V}^{2}}}{2R}\]             ... (i) (ii) In parallel: potential difference across each resistance will be\[V\] So, power consumed in each resistance is                 \[P=\frac{{{V}^{2}}}{R}\] So total power consumed in two resistance is                 \[{{P}_{2}}=\frac{{{V}^{2}}}{R}+\frac{{{V}^{2}}}{R}=\frac{2{{V}^{2}}}{R}\]                              ? (ii) Hence, ratio in two cases                 \[=\frac{{{P}_{1}}}{{{P}_{2}}}\]                 \[=\frac{{{V}^{2}}\times R}{2R\times 2{{V}^{2}}}\]                 \[=\frac{1}{4}\]


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