NEET Physics Transmission of Heat NEET PYQ-Transmission Of Heat

  • question_answer
    A black body is at \[727{}^\circ C\]. It emits energy at a rate which is proportional to:               [AIPMT (S) 2007]

    A) \[{{(727)}^{2}}\]

    B)                   \[{{(1000)}^{4}}\]

    C)  \[{{(1000)}^{2}}\]

    D)                   \[{{(727)}^{4}}\]

    Correct Answer: C

    Solution :

    Key Idea: Amount of heat energy radiated per second by unit area of a black body is directly proportional to fourth power of absolute temperature.
                According to Stefan's law,
                \[E\,\propto \,\,{{T}^{4}}\]
                or         \[E=\sigma {{T}^{4}}\]
                where \[\sigma \] is constant of proportionality and called Stefan's constant. Its value is
                \[5.67\times {{10}^{-8}}\,W{{m}^{-2}}\,{{K}^{-4}}\]
                Hence,  \[E\,\propto \,\,{{(727+273)}^{4}}\]     
                \[\Rightarrow \]   \[E\,\propto \,{{(1000)}^{4}}\]
                Note:    If the body at temperature T is surrounded by a body at temperature \[{{T}_{0}},\] then  Stefan’s law is \[E=\sigma ({{T}^{4}}-T_{0}^{4})\]
    This statement is called Stefan-Boltzmann law:


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