JEE Main & Advanced AIEEE Solved Paper-2002

  • question_answer
    Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively. The ratio of the energy radiated per second by the first sphere to that by the second is   AIEEE  Solved  Paper-2002

    A) \[1:1\]        

    B)                           \[16:1\]

    C) \[4:1\]                     

    D)           \[1:9\]

    Correct Answer: A

    Solution :

    Energy radiated per second by a body which has surface area A at temperature T is given by Stefan's law,              \[E=\sigma A{{T}^{4}}\] Therefore.   \[\frac{{{E}_{1}}}{{{E}_{2}}}={{\left( \frac{{{r}_{1}}}{{{r}_{2}}} \right)}^{2}}{{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{4}}={{\left( \frac{1}{4} \right)}^{2}}{{\left( \frac{4000}{2000} \right)}^{4}}\]              (since, bodies are of same material \[{{\sigma }_{1}}={{\sigma }_{2}}\])    \[\therefore \frac{{{E}_{1}}}{{{E}_{2}}}=\frac{16}{16}=\frac{1}{1}=1.1\] 


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