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AMU Medical AMU Solved Paper-2006

  • question_answer
    A body at a temperature of \[727{}^\circ C\] and has surface area 5 cm2, radiates 300 J of energy each minute. The emissivity is (Given : Boltzmann constant \[=5.67\times {{10}^{-8}}W{{m}^{2}}{{K}^{4}})\]

    A)  \[e\]=0.18                         

    B)  \[e\]=0.02

    C)  \[e\]=0.2                           

    D)  \[e\]=0.15

    Correct Answer: A

    Solution :

    \[Q=E\] At \[=e\,\sigma \,({{T}^{4}}-T_{0}^{4})\] At where t = time To = temperature of surrounding When, \[T>{{T}_{0}}\] \[Q=e\,\,\sigma {{T}^{4}}\] At \[300=e\times (5.67\times {{10}^{-8}})\,\,{{(1000)}^{4}}\]                                 \[(5.00\times {{10}^{-4}})\,(60)\] e = 0.18


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