- #1
yyouth24
- 16
- 0
Why does passing current through Wolfram filament, heats the Wolfram filament in light bulb? What happens with the electrons?
Why Does Passing Current Heat Wolfram Filament in Light Bulb?
- Context: High School
- Thread starter yyouth24
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Discussion Overview
The discussion centers around the heating of a tungsten filament in a light bulb when electric current passes through it. Participants explore the mechanisms of heat generation, material properties, and the comparison of tungsten with other materials like iron.
Discussion Character
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants propose that Ohmic heating is responsible for the heating of the tungsten filament, where electrons collide with the filament's ions, transferring kinetic energy as heat.
- Others discuss the properties of tungsten, noting its high density, high melting point, low thermal expansion coefficient, and low reactivity, which contribute to its effectiveness in light bulb applications.
- A participant questions why tungsten releases more energy than iron when current passes through it, prompting further exploration of material properties.
- One participant humorously expresses confusion over the term "Wolfram" and clarifies that it refers to tungsten.
- A later reply raises a question about the conditions under which tungsten would turn into a liquid and whether the atoms would need to be disintegrated.
Areas of Agreement / Disagreement
Participants generally agree on the role of Ohmic heating and the properties of tungsten, but there are questions and uncertainties regarding the comparison with iron and the specifics of phase changes in tungsten.
Contextual Notes
The discussion includes assumptions about material properties and lacks detailed exploration of the underlying physics of phase transitions and atomic behavior at high temperatures.
- #2
Archduke
- 59
- 1
It's down to Ohmic heating. The electrons collide with the ions of the filament, and pass on its kinetic energy to the ions in the form of heat energy, which is proportional to the square of the current multiplied by the resistance of the filament.
- #3
yyouth24
- 16
- 0
And why let's say, the Wolfram filament is releasing more energy (when current passes through it) than the iron?Archduke said:
- #4
Danger
Gold Member
- 9,805
- 251
Welcome to PF, Yyouth.
First off, thank you too much for driving me half nuts with your question. (
) I spent a couple of hours trying to figure out who the hell Wolfram was and how his filament differed from a normal tungsten one. 
Anyhow, tungsten is a lot denser than iron, so internal particle collisions are far more numerous. Its other properties, though, are what make it so incredibly perfect for lightbulb use. To start with, it has one of the highest melting points of any metal. Combined with its very low thermal expansion coefficient, it allows bulbs to be run far hotter than could be achieved with other materials. That low expansion also allows a very long piece of wire to be put into a very small space. Filaments are typically double-coiled, wherein the original coiled wire is coiled again. The easiest way that I can think of to clarify that is if you were to take a long spring such as from a ball-point pen and wrap it around a toothpick. That 1/4" long filament would probably be over a metre long if stretched out. Tungsten is also very unreactive, so impurities that might sneak into the argon atmosphere of a bulb are less likely to cause failure.
First off, thank you too much for driving me half nuts with your question. (
) I spent a couple of hours trying to figure out who the hell Wolfram was and how his filament differed from a normal tungsten one. Anyhow, tungsten is a lot denser than iron, so internal particle collisions are far more numerous. Its other properties, though, are what make it so incredibly perfect for lightbulb use. To start with, it has one of the highest melting points of any metal. Combined with its very low thermal expansion coefficient, it allows bulbs to be run far hotter than could be achieved with other materials. That low expansion also allows a very long piece of wire to be put into a very small space. Filaments are typically double-coiled, wherein the original coiled wire is coiled again. The easiest way that I can think of to clarify that is if you were to take a long spring such as from a ball-point pen and wrap it around a toothpick. That 1/4" long filament would probably be over a metre long if stretched out. Tungsten is also very unreactive, so impurities that might sneak into the argon atmosphere of a bulb are less likely to cause failure.
- #5
Cundo007
- 3
- 0
Hey.. this not a reply because I am new i this forum... i need help... how can i post a questions... sorry for the trouble...
- #6
Danger
Gold Member
- 9,805
- 251
Welcome to PF, Cundo.
Go to the appropriate sub-forum (Classical Physics is this one). Just above the main body, there's a button that says 'New Thread'. Click on that, and you'll be prompted to enter a title and whatever text you want. When you're satisfied with your post, click on the 'Submit' button at the bottom. If you're unsure of what sub-forum it belongs in, post it in General Discussion and a Mentor will move it to where it should be.
Go to the appropriate sub-forum (Classical Physics is this one). Just above the main body, there's a button that says 'New Thread'. Click on that, and you'll be prompted to enter a title and whatever text you want. When you're satisfied with your post, click on the 'Submit' button at the bottom. If you're unsure of what sub-forum it belongs in, post it in General Discussion and a Mentor will move it to where it should be.
- #7
Cundo007
- 3
- 0
Thankss... i got a feeling ill be listening from you again...
- #8
Danger
Gold Member
- 9,805
- 251
Don't let it become a habit; I make up half of the stuff that I post here. 
- #9
yyouth24
- 16
- 0
Ok, thank you very much.Danger said:Welcome to PF, Yyouth.
First off, thank you too much for driving me half nuts with your question. (
Anyhow, tungsten is a lot denser than iron, so internal particle collisions are far more numerous. Its other properties, though, are what make it so incredibly perfect for lightbulb use. To start with, it has one of the highest melting points of any metal. Combined with its very low thermal expansion coefficient, it allows bulbs to be run far hotter than could be achieved with other materials. That low expansion also allows a very long piece of wire to be put into a very small space. Filaments are typically double-coiled, wherein the original coiled wire is coiled again. The easiest way that I can think of to clarify that is if you were to take a long spring such as from a ball-point pen and wrap it around a toothpick. That 1/4" long filament would probably be over a metre long if stretched out. Tungsten is also very unreactive, so impurities that might sneak into the argon atmosphere of a bulb are less likely to cause failure.
- #10
yyouth24
- 16
- 0
And when the element will be turned into liquid? Should the atoms be totally disintegrated?
Last edited:
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