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BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    Two bulbs have wattage 250 W and 100 W respectively, each rated at 220 V. The ratio of resistances between the two bulbs will be:

    A)  2 : 5       

    B)  5 : 2                      

    C)  3 : 4                      

    D)         4 : 3

    Correct Answer: A

    Solution :

                                    Resistance of bulb \[R=\frac{{{V}^{2}}}{P}\] As V is constant hence, \[R\propto \frac{1}{P}\]                 or            \[\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{{{P}_{2}}}{{{P}_{1}}}\] Here, \[{{P}_{1}}=250\,W,{{P}_{2}}=100\,W\] \[\therefore \]  \[\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{100}{250}=\frac{2}{5}\]


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