Homework Help: Resistance and Heating Effect

1. Feb 23, 2012

Peter G.

I understand how the collisions between positive ions and electrons generate heat when a current runs through a wire. I, therefore understand that as temperature increases, collisions are more frequent, translating into a higher resistance. It then follows that, an increased resistance, due to the fact the electrons can't flow as freely, results in increased collisions and an increase in temperature? In other words, an increased resistance equals a greater heating effect? I ask this because, from my understanding, a large current leads to a heating effect due to more collisions but, doesn't resistance hinder the flow of electrons? I tested this once with a piece of wire. I made the wire very short (very low resistance) and when I turned on the power it was cut in half!

Any ideas?

Thanks!

2. Feb 23, 2012

rktpro

You might be interested in Joule's calorimeter experiments for deriving the Joule's Heating Law. Google for it.
And, yes, increase in temperature means less average relaxation time and hence more resistance.

3. Feb 24, 2012

Peter G.

Cool! Will look for it. But I read somewhere that the greatest the resistance, the greater the heating effect. How, if a larger current triggers a large heating effect?