JEE Main & Advanced Physics Transmission of Heat Question Bank Radiation Stefan's law

  • question_answer
    A sphere at temperature 600K is placed in an environment of temperature is 200K. Its cooling rate is H. If its temperature reduced to 400K then cooling rate in same environment will become           [CBSE PMT 1999; BHU 2001]

    A)            (3/16)H                                   

    B)            (16/3)H

    C)            (9/27)H                                   

    D)            (1/16)H

    Correct Answer: A

    Solution :

                       Rate of cooling \[\propto ({{T}^{4}}-T_{0}^{4})\] Þ \[\frac{H}{H'}=\frac{(T_{1}^{4}-T_{0}^{4})}{(T_{2}^{4}-T_{0}^{4})}=\]\[\frac{{{400}^{4}}-{{200}^{4}}}{{{600}^{4}}-{{200}^{4}}}\]            or \[H'=\frac{(16+4)(16-4)H}{(36+4)(36-4)}\]\[=\frac{3}{16}H\]


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