Calculate Heat Loss from Copper Sphere of 8cm Diameter

Click For Summary

Discussion Overview

The discussion revolves around calculating the net rate of heat loss from a blackened copper sphere with an 8cm diameter, heated to 147 degrees C and suspended in a room at 25 degrees C. The focus includes theoretical aspects of heat transfer and assumptions regarding material properties.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes the lack of constants such as Stefan's constant and emissivity, questioning how to proceed with the calculation.
  • Another participant suggests treating the sphere as a blackbody with an emissivity of 1, allowing for the use of the Stefan-Boltzmann law to calculate power radiated per unit area.
  • A participant expresses intent to attempt the calculation later, indicating engagement with the problem.
  • There is a question about whether the temperature used in calculations should be the temperature difference or the actual temperature of the blackbody.
  • Another participant clarifies that the temperature in question refers to the temperature of the object itself.

Areas of Agreement / Disagreement

The discussion contains some agreement on treating the sphere as a blackbody, but there is uncertainty regarding the constants needed for the calculation and the interpretation of temperature in the context of the heat loss calculation.

Contextual Notes

Participants have not resolved the issue of missing constants, and there is ambiguity regarding the assumptions about the temperature used in the calculations.

EIRE2003
Messages
107
Reaction score
0
A copper sphere of 8cm diameter is blackened and suspended from the ceiling by a fine thread in a room kept at 25 degrees C. The sphere is then heated to a temp of 147 degrees C.
Calculate the net rate of heat loss by the sphere.

Im not given any constants such as stefans or the emissivity of the body, so how can this be calculated?
 
Science news on Phys.org
The sphere is copper (i.e. great thermal conductor) so you can assume its temperature is constant throughout its volume. Treat it as a blackbody (emissivity = 1) which allows you to calculate the power radiated per unit area as [itex]\sigma T^4[/itex].
 
Thank You I'll try it out when i get up out of the scratcher!
 
Is the Temperature the difference in the temperature or the temperature of the black body itself?
 
It's the temperature of the object itself!
 

Similar threads

  • · Replies 16 ·
Replies
16
Views
5K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 3 ·
Replies
3
Views
10K
  • · Replies 3 ·
Replies
3
Views
5K
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
12K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 5 ·
Replies
5
Views
14K
  • · Replies 1 ·
Replies
1
Views
13K