BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    At 127°C radiated energy is \[2.7\,\times {{10}^{-3}}\,J/s\]. At what temperature radiated energy is \[4.32\,\times {{10}^{6}}J/s\]?

    A)  400 K                                   

    B)  4000 K 

    C)         80000 K       

    D)         40000 K

    Correct Answer: C

    Solution :

                    Energy radiated from a body \[Q=Ae\sigma {{T}^{4}}t\]                 \[\Rightarrow \]               \[\frac{{{Q}_{2}}}{{{Q}_{1}}}={{\left( \frac{{{T}_{2}}}{{{T}_{1}}} \right)}^{4}}\]                 \[\Rightarrow \]               \[\frac{{{T}_{2}}}{{{T}_{1}}}={{\left( \frac{{{Q}_{2}}}{{{Q}_{1}}} \right)}^{1/4}}={{\left( \frac{4.32\times {{10}^{6}}}{2.7\times {{10}^{-3}}} \right)}^{1/4}}\]                                 \[\frac{{{T}_{2}}}{400}={{\left( \frac{16\times 27}{27}\times {{10}^{8}} \right)}^{1/4}}=2\times {{10}^{2}}\]                 \[\Rightarrow \]               \[{{T}_{2}}=200\times 400=80000\,K\]


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