Temperature of a thin bulb filament

Click For Summary

Discussion Overview

The discussion revolves around the relationship between the temperature of a thin bulb filament and its length (L) and radius (r). Participants explore how these parameters influence temperature, particularly in the context of the Stefan-Boltzmann law and Joule-Lenz law.

Discussion Character

  • Homework-related, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant states that the temperature T is proportional to r^(1/4) and L^(-1/2) under constant voltage conditions.
  • Another participant reiterates the relationship T~r^(1/4)L^(-1/2) and suggests using the Stefan-Boltzmann law while neglecting ambient temperature.
  • A participant expresses confusion regarding the application of the Stefan-Boltzmann law, noting that it only relates power radiated to temperature and questions how L and r are incorporated.
  • Another participant clarifies that L and r affect both the radiated power (as per Joule-Lenz law) and the surface area of the filament, which in turn influences the radiated power density.
  • One participant indicates they have understood the concept after the discussion.
  • A final comment suggests that the question was more appropriate for the homework forum and that using a homework template would have been beneficial.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the relationship between temperature, length, and radius, with some confusion remaining about the application of the Stefan-Boltzmann law. There is no clear consensus on the derivation of the temperature relation.

Contextual Notes

Participants have not fully resolved how the parameters L and r are integrated into the temperature calculation, and there are unresolved assumptions regarding the application of the Stefan-Boltzmann law and the context of the problem.

Baibhab Bose
Messages
34
Reaction score
3
In my assignment question, the length L and radius r is given and asked to find out how the Temperature of a thin bulb filament which depends on those two parameters. and the answer is r^(1/4)*L^(-1/2). I can't figure out how. Which relation is involved?
 
Science news on Phys.org
For constant voltage at ends,
T~r1/4L-1/2
Use Stefan-Boltzmann law and neglect ambient temperature.
 
trurle said:
For constant voltage at ends,
T~r1/4L-1/2
Use Stefan-Boltzmann law and neglect ambient temperature.
I still can't get this. Stefan Boltzmann law states only Power radiated= σT^4. But where do we get the L and r?
 
Baibhab Bose said:
I still can't get this. Stefan Boltzmann law states only Power radiated= σT^4. But where do we get the L and r?
L and R affect both radiated power (by Joule-Lenz law) and surface area of filament which affect radiated power density
 
Okay! Got it! Thank you so much!
 
This question should have been asked in the homework forum. Filling out the homework template would have been useful.

Thread closed,
 

Similar threads

Undergrad How to determine temperature of filament?
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Edison effect for Incandescent Bulb?
  • · Replies 3 ·
Replies
3
Views
5K
Undergrad How Does Temperature Affect Wire Tension at Constant Length?
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Empirical temperature scales using different thermometers
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad Energy Flow From Battery to the Light Bulb
  • · Replies 16 ·
Replies
16
Views
5K
Undergrad Simple thought experiment with Stefan-Boltzmann law: energy
  • · Replies 7 ·
Replies
7
Views
1K
Graduate Uncovering the Source of Extra 267 J in Standard Incandescent Light Bulb
  • · Replies 34 ·
2
Replies
34
Views
4K
Undergrad Finding the temperature of light bulb filament?
  • · Replies 2 ·
Replies
2
Views
12K
Final Temperature of a Lightbulb filament
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad How to understand experiment to measure heat capacity of solid?
  • · Replies 1 ·
Replies
1
Views
2K