Radiation from a cube at 189 °C

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Homework Help Overview

The discussion revolves around a thermodynamics problem involving radiation from a cube. The original poster attempts to calculate the radiative heat transfer rate of a cube when its temperature is increased from 102 °C to 189 °C, using the Stefan-Boltzmann law.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of the relevant equation for radiative heat transfer and question the correctness of the original poster's calculations. There is a focus on ensuring the use of absolute temperatures and the implications of unit consistency.

Discussion Status

Some participants have provided guidance regarding the need for absolute temperature in the calculations and have pointed out potential issues with the problem statement's clarity. Multiple interpretations of the problem's requirements are being explored.

Contextual Notes

There is a noted lack of complete information in the problem statement, particularly regarding the expected answer choices. Additionally, the original poster's concerns about the correctness of their answer are not fully explained, leading to further questioning of assumptions.

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Homework Statement
A cube at 102 °C radiates heat at a rate of 64 J/s. If its surface temperature is increased to 189 °C, the rate at which it will now radiate is closest to
Relevant Equations
P2/P1=(T2/T1)^4
I have tried to use the above equation.
P2/64=(189/102)^4
P2=754.4431
But I don't know why the answer is wrong. Please help!
 
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Wath out your units
 
Tinkylo said:
Homework Statement:: A cube at 102 °C radiates heat at a rate of 64 J/s. If its surface temperature is increased to 189 °C, the rate at which it will now radiate is closest to
Relevant Equations:: P2/P1=(T2/T1)^4

I have tried to use the above equation.
P2/64=(189/102)^4
P2=754.4431
But I don't know why the answer is wrong. Please help!
First, this does not appear to be a complete problem statement since you trail off with "the rate at which it will now radiate is closest to " which looks like it should be followed by choices, plus you say the answer is wrong but you give no indication WHY you think it is wrong, which again seems to imply that there are choices for the answer and your answer isn't any of them.

Second, that subject line is terrible. Of course you have a problem or question. That's what the homework section is for, but why make people guess what KIND of problem instead of saying something like "need help with a thermodynamics problem" ?
 
Tinkylo said:
Relevant Equations:: P2/P1=(T2/T1)^4
The temperatures here are absolute temperatures.
 
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phinds said:
Second, that subject line is terrible. Of course you have a problem or question. That's what the homework section is for, but why make people guess what KIND of problem instead of saying something like "need help with a thermodynamics problem" ?
Agreed. I fixed the thread title to make it actually describe the problem, instead of being an empty statement "Please help with the Question! ".
 
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