Wire supplying current to a filament lamp doesnt get hot?

[Dixanadu]

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 :)

 

[nsaspook]

http://www.allaboutcircuits.com/textbook/direct-current/chpt-2/calculating-electric-power/

What is the resistance of the wire to the lamp?

 

[ZapperZ]

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.

 

[CWatters]

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.