Why Do Light Bulbs Blow When You Turn Them On?

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Homework Help Overview

The discussion revolves around the phenomenon of light bulbs blowing when turned on, specifically relating to resistance and temperature as observed in a classroom experiment. The original poster seeks to understand the underlying reasons for this occurrence.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between current, resistance, and temperature, questioning how resistance changes with temperature and its impact on the light bulb's failure. Some participants attempt to clarify the mechanics of the filament's behavior under different conditions.

Discussion Status

There is an ongoing exploration of the concepts involved, with some participants providing insights into the mechanics of the filament and the effects of temperature and current. However, the discussion has not reached a definitive conclusion.

Contextual Notes

The original poster expresses uncertainty about relevant equations and seeks guidance on where to find more information. The discussion includes assumptions about the behavior of materials under varying temperatures and the implications for light bulb operation.

_Muddy_
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Homework Statement



We did an experiment in class abvout resistance and temperature. The teacher told us to find out why light bulbs usually blow when you turn on the light. It must be related to the experiment we did which was seeing how resistance changed with temperature

Homework Equations


I'm not sure if there are any, If there are please tell me


The Attempt at a Solution


I have no idea why, and i wouldn't know where to look on the internet

thanks

_Muddy_
 
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The light bulb fails because the current through the filament is too large.
The current depends on the resistance
How does the resistance of metal change with temperature ?
 
mgb_phys said:
The light bulb fails because the current through the filament is too large.
The current depends on the resistance
How does the resistance of metal change with temperature ?

The higher the temperature the higher the resistance.

So then, the light bulb fails because the current through the filament is too large. The resistance is too low. So the temperature is too high. Is that correct? What actually happens to the filament, does it break? Why would a high temperature/ high current make the light bulb fail?
 
The filament is a thin metal wire - rather like a fuse.
When the filament is cold the resistance is lower and so the currentis higher.

The current heats the wire which expands which puts a mechanical strain on it.
Also when the light is first turned on is the greatest temperature difference and so the greatest strain - this is probablyy more important than the resistance in reality
 
thanks a lot for that, I'm pleased and my teacher should be pleased aswell
 

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