RAJASTHAN ­ PET Rajasthan PET Solved Paper-2010

  • question_answer
    Two spheres P and Q, of same colour having radii 8 cm and 2 cm are maintained at temperature \[127{}^\circ C\]and\[527{}^\circ C\]respectively. The ratio of energy radiated by P and Q is

    A)  0.054          

    B)  0.0034

    C)  1                

    D)  2

    Correct Answer: A

    Solution :

     Total energy radiated from a body \[Q=A{{\varepsilon }_{0}}{{T}^{4}}t\] \[\Rightarrow \] \[Q\propto A{{T}^{4}}\propto {{r}^{2}}{{T}^{4}}\] \[(\because A=4\pi {{r}^{2}})\] \[\therefore \] \[\frac{{{Q}_{p}}}{{{Q}_{Q}}}={{\left( \frac{{{r}_{p}}}{{{r}_{Q}}} \right)}^{2}}{{\left( \frac{{{T}_{p}}}{{{T}_{Q}}} \right)}^{4}}\] \[={{\left( \frac{8}{2} \right)}^{2}}{{\left( \frac{273+127}{273+527} \right)}^{4}}=1\]


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