Archived Thermal Diffusion with Heat Source

rabbit44

1. Homework Statement
A cylindrical wire of thermal conductivity k, radius a and resistivity p uniformly
carries a current I. The temperature of its surface is fixed at T0 using water cooling.
Show that the temperature T(r) inside the wire at radius r is given by
T(r) = T0 + p(I^2)(a^2 - r^2)/4pi^2a^4k

2. Homework Equations
del squared(T) = (c/k)dT/dt - H/k

Where H is heat generated per unit volume

3. The Attempt at a Solution
I took the system to be in a steady state as the temperature is fixed. So:

d2T/dr2 = -H/k

I took H = I^2 (pl/A)(1/lA)
= I^2p/pi^2a^4

Subbing this into my differential equation and integrating twice wrt r, I get:

T = -(I^2.p.r^2)/(2pi^2.a^4.k) + ba + c

Where b and c are integration constants. I think b must be zero but am not sure why. Then putting in T=T0 at r=a I would get a close answer but with a 2 on the bottom of the second term instead of a 4.

Where did I go wrong?!?

Thanks

Last edited:
Related Introductory Physics Homework Help News on Phys.org

mrb132

"Thermal Diffusion with Heat Source"

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving