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A metal rod at a temperature of 150 degree Celsius, radiates energy at arate of 20W. If its temperature is increased to 300 degree celsius,then it will radiate at a rate of about?
1. 40.8 W
2. 17.5 W
3. 68.3 W
4. 37.2 W
Please explain the answer as well.

Asked by mamalinanda1998 15th May 2016, 4:27 PM
Answered by Expert
Answer:
begin mathsize 12px style According space to space the space Stefan apostrophe straight s space law comma space straight E space equals space straight sigma space straight T to the power of 4
When space the space temperature space of space the space body space is space raised space from space straight T space to space straight T apostrophe comma space then space the space new space rate space of space emission space will space be space
straight E apostrophe space equals space straight sigma apostrophe space straight T apostrophe to the power of 4 space
fraction numerator straight E apostrophe over denominator straight E end fraction equals fraction numerator straight T apostrophe over denominator straight T end fraction
fraction numerator straight E apostrophe over denominator 20 space straight W space end fraction equals fraction numerator left parenthesis 573 right parenthesis to the power of 4 space straight K over denominator left parenthesis 423 right parenthesis to the power of 4 space straight K end fraction
On space solving space we space get
straight E apostrophe space equals space 67.3 space straight W end style
Answered by Expert 16th May 2016, 7:17 PM
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