Heat is flowing in steady state from temperature $$100oC$$ to temperature $$0oC$$ through a rod of length l, cross sectional area A and thermal conductivity K at a rate Q. When another rod of length $$2l$$, $$cross-sectional$$ area A and thermal conductivity $$K/2$$ is joined end to end to the above rod to make a composite rod of length $$3l$$ whose ends are maintained at $$100oC$$ and $$0oC$$, rate of heat conduction at steady state is

Question

Heat is flowing in steady state from temperature $$100oC$$ to temperature $$0oC$$  through a rod of length l, cross sectional area A and thermal conductivity K at a rate Q. When another rod of length $$2l$$, $$cross-sectional$$ area A and thermal conductivity $$K/2$$ is joined end to end to the above rod to make a composite rod of length $$3l$$ whose ends are maintained at $$100oC$$ and $$0oC$$, rate of heat conduction at steady state is

Infinity Learn · Accepted Answer

For the first rod, thermal resistance $$R=lKA=100-0QFor$$ the second rod, thermal resistance R'$$=2lK/2A=4lKA=4RSo$$ equivalent thermal resistance $$Re=R+R$$'$$=R+4R=5R$$∴Q'$$=100-0Re=1005R=15$$ x Q

Start JEE / NEET / Foundation preparation at rupees 99/day !!

Detailed Solution

Get Expert Academic Guidance – Connect with a Counselor Today!