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Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2005

  • question_answer
    Two bulbs of 500 W and 200 W are manufactured to operate on 220 V line. The ratio of heat produced in 500 W and 200 W, in two cases, when firstly they are joined in parallel and secondly in series, will be

    A)  5/2,2/5                               

    B)  5/2,5/2

    C)  2/5, 5/2                              

    D)  2/5, 2/5

    Correct Answer: A

    Solution :

    In parallel \[\therefore \]  \[{{H}_{1}}=\frac{{{V}^{2}}}{R}t\]                 \[=\frac{{{(220)}^{2}}}{\frac{{{(220)}^{2}}}{500}}=500t\]                 \[{{H}_{2}}=\frac{{{(220)}^{2}}}{\frac{{{(220)}^{2}}}{200}}t=200t\]                 \[\frac{{{H}_{1}}}{{{H}_{2}}}=\frac{500t}{200t}=\frac{5}{2}\] In series                 \[{{H}_{1}}={{I}^{2}}RT\]                 \[={{I}^{2}}\frac{{{(220)}^{2}}}{500}\times t\]                 \[=\frac{{{(220)}^{2}}}{200}t\]                 \[=\frac{{{(220)}^{2}}}{500}\times \frac{200}{{{(220)}^{2}}}\]                 \[\frac{{{H}_{1}}}{{{H}_{2}}}=\frac{2}{5}\]


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