# Physics

posted by Chelsea

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.

1. Damon

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)

2. Damon

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)

3. Chelsea

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!

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