- #1
luxux
- 10
- 1
Hello,
I was giving a random thought to Ohm's Laws and thermal dilation.
As a general rule we are told that ohmic resistors will increase their resistivity if their temperature increases. Does this take into account the fact that its dimensions will change due to thermal dilation?
This would make sense given the similarity between the mathematical expressions of the two phenomena.
The usual conclusion is that therefore resistance of a wire of that material must increase.
But shouldn't we take into account the fact that by warming up a wire we are also increasing its length and cross-sectional area? The former effect would contribute to an increase in resistance, but the latter would reduce the resistance.
Do we usually say that increasing temperature increases resistivity and thus resistance only because we neglect thermal dilation effects? Or is it because since the ratio length/c.s. area is usually high the reduction of resistance due to an increase in c.s. area is much smaller than its increase due to the increase in length?
I was giving a random thought to Ohm's Laws and thermal dilation.
As a general rule we are told that ohmic resistors will increase their resistivity if their temperature increases. Does this take into account the fact that its dimensions will change due to thermal dilation?
This would make sense given the similarity between the mathematical expressions of the two phenomena.
The usual conclusion is that therefore resistance of a wire of that material must increase.
But shouldn't we take into account the fact that by warming up a wire we are also increasing its length and cross-sectional area? The former effect would contribute to an increase in resistance, but the latter would reduce the resistance.
Do we usually say that increasing temperature increases resistivity and thus resistance only because we neglect thermal dilation effects? Or is it because since the ratio length/c.s. area is usually high the reduction of resistance due to an increase in c.s. area is much smaller than its increase due to the increase in length?