A composite block is made of slabs A, B, C, D and E of different thermal conductivities (given in terms of a constant K) and sizes (given in terms of length, L) as shown in the figure. All slabs are of same width. Heat ‘Q’ flows only from left to right through the blocks. Then in steady state:

Question

G1 Physics · Accepted Answer

In steady conduction, heat current is H=kAΔT/L. Treat each segment as a thermal resistance Rₜₕ=L/(kA); series resistances add and parallel heat currents add. Evaluating the given data/statements gives A: heat flow through A and E slabs are same.; C: temperature difference across slab E is smallest.; D: heat flow through C = heat flow through B + Heat flow through D.. Therefore the correct answer is A, C, D. Source answer key also lists ABCD as an accepted alternative.