A bar of aluminum (bar A) is in thermal contact with a bar of iron (bar B) of the same length and area. One end of the compound bar is maintained at Th = 75.5°C while the opposite end is at 30.0°C. Find the temperature at the junction when the energy flow reaches a steady state.

Answer 1

conductivity iron = FE
conductivity al = AL

temp difference over iron = 75.5 - T
temp difference over Al = T - 30

(75-T) (FE) proportional to Q
(T-30) (AL) same proportional to q because areas and lengths the same
so same Q through each
(75-T)(FE) = (T-30) (AL)

Answer 2

by the way the ratio of AL/FE is about 136/46
(you don't need units here because all you need is the ratio)

Answer 3

Thanks for your help! The only thing is that the AL and FE need to be switched around and then I got the correct answer. There is a picture that I forgot to post that has Aluminum by the 75.5 and 30 next to the Iron. Thanks again!

Answer 4

Thanks for the help