Heat transfer through two metal bars

[kidsmoker]

Homework Statement

A steel bar 10cm long is welded end to end to a copper bar 20cm long. Both bars are insulated perfectly on their sides. Each bar has a square cross section, 2cm on a side. The free end of the steel bar is maintained at 100 celsius and the free end of the copper bar is maintained at 0 celsius. Find the temperature at the junction of the two bars.

The attempt at a solution

The problem is a worked example so I can see the method for solving it. But I don't understand why they take the heat currents through the two bars to be equal? Would someone be able to explain it to me? :)

Thanks!

 

[tiny-tim]

… maintained … maintained …

I don't understand why they take the heat currents through the two bars to be equal?

Hi kidsmoker!

Read every word in exam questions …

the word "maintained" tells you that the system has reached equilibrium …

so heat in must equal heat out at all points.