Here, we have to find out the temperature difference across the slab A.
We have steady state
Rate of heat flow through copper = Rate of heat flow through steel
We have
The coefficient of thermal conductivity of a substance
k =
where Q - heat conducted normally
d = length of the rod
A - area of the cross section
Q1 and
Q2 - Temperatures at two ends
i.e., Q =
Let θ be the temperature at the junction
Therefore, rate of heat flow
P =
=