1.

Two solid sphere of copper have radii 10 cm and 8 cm respectively. Their temperature are 227^(@)C and 127^(@)C respectively they are allowed to cool by radiation in a room of temperature 27^(@)C then the initial rates of heat los are in the ratio

Answer»

`(85)/(14)`
`(34)/(7)`
`(7)/(34)`
`(14)/(85)`

Solution :`(((DQ)/(DT))_(1))/(((dQ)/(dt))_(2))=(T_(1)^(4))/(T_(2)^(4))=(625)/(256)=2.44`.


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