Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    Two bulbs consume same power when operated at 200 V and 300 V respectively. When these bulbs are connected in series across a DC source of 500 V, then

    A)  ratio of potential differences across them is 3/2

    B)  ratio of potential differences across them is 9/4

    C)  ratio of powers consumed across them is 4/9 

    D)  ratio of powers consumed across them is 2/3

    Correct Answer: C

    Solution :

                    \[P=\frac{{{V}^{2}}}{R}\] \[\therefore \]  \[R=\frac{{{V}^{2}}}{P}\] or            \[R\propto {{V}^{2}}\] i.e.,        \[\frac{{{R}_{1}}}{{{R}_{2}}}={{\left[ \frac{200}{300} \right]}^{2}}=\frac{4}{9}\] When connected in series potential drop and power consumed are in the ratio of their resistances. So.                 \[\frac{{{P}_{1}}}{{{P}_{2}}}=\frac{{{V}_{1}}}{{{V}_{2}}}=\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{4}{9}\]


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