BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    Two identical heaters of 220 V, 1000 W are placed in parallel with each other across 220 V line, then the combined power is:

    A)  1000 W                               

    B)         2000 W

    C)         500 W                                  

    D)         4000 W

    Correct Answer: B

    Solution :

    Let the resistance of the two heaters be denoted by \[{{R}_{1}}\]and \[{{R}_{2}}.\] Then,                    \[{{R}_{1}}=\frac{{{V}^{2}}}{{{P}_{1}}}\]                                 \[{{R}_{2}}=\frac{{{V}^{2}}}{{{P}_{2}}}\] In parallel combination of resistances,                                 \[\frac{1}{{{R}_{p}}}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}\]                                 \[\frac{{{P}_{p}}}{{{V}^{2}}}=\frac{{{P}_{1}}}{{{V}^{2}}}+\frac{{{p}_{2}}}{{{V}^{2}}}\]                                 \[{{P}_{p}}={{P}_{1}}+{{P}_{2}}\] Given,     \[{{P}_{1}}=1000\,W\]                                 \[{{P}_{2}}=1000\,W\]                 \[\therefore \]  \[{{P}_{p}}=1000+1000\]                 Hence,  \[{{P}_{p}}=2000\,W\]


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