Wire supplying current to a filament lamp doesnt get hot?

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Discussion Overview

The discussion revolves around the question of why the wire supplying current to a filament lamp does not heat up significantly, while the filament itself does. This inquiry touches on concepts of electrical resistance, material properties, and the behavior of different components in a circuit.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the resistance of the wire connected to the lamp, suggesting that understanding this could clarify why the wire does not heat up.
  • Another participant emphasizes the difference in material and thickness between the filament (made of thin tungsten) and the supply wire (made of thicker copper), implying that these factors contribute to the heating behavior.
  • A further comment raises the durability of filaments in different types of bulbs, hinting at the effects of vibration and shock on filament integrity compared to the wire.

Areas of Agreement / Disagreement

Participants appear to share an interest in understanding the thermal behavior of the wire and filament but do not reach a consensus on the specific reasons or mechanisms involved. Multiple viewpoints are presented without resolution.

Contextual Notes

Participants reference the resistivity of materials and the physical characteristics of the filament and wire, but do not provide detailed calculations or definitions, leaving some assumptions and dependencies unaddressed.

Dixanadu
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Hi everyone,

So one of my students has asked me a question which I'm not sure how to answer. The question is: Why does the wire that supplies current to the filament lamp in a light bulb not heat up, even though the filament itself does?

Please let me know your thoughts! Thank you :)
 
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http://www.allaboutcircuits.com/textbook/direct-current/chpt-2/calculating-electric-power/

What is the resistance of the wire to the lamp?
 
Dixanadu said:
Hi everyone,

So one of my students has asked me a question which I'm not sure how to answer. The question is: Why does the wire that supplies current to the filament lamp in a light bulb not heat up, even though the filament itself does?

Please let me know your thoughts! Thank you :)

To emphasize what nsaspook has said, why do you think that the filament in the light bulb is often made of very thin tungsten, whereas the wire supplying the current and connected to the light bulb is made of thicker copper? Look up the resistivity of each as a start.

Zz.
 
Once you understand the above you might be able to work out why the filament in a car headlight bulb (say 50W,12V) doesn't break easily? After all they are subjected to high levels of vibration and shock. If you have ever handled an old a domestic light bulb (say 50W, 220V) you will know that it's very easy to break the filament - simply removing the bulb and putting it down on a table can be enough.
 

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