A cylinder of radius R made of a material of thermal conductivity 7 is surrounded by a cylindrical shell of inner radius R and outer radius 2R. The shell is made of a material of thermal conductivity 3. The two ends of the combined system are maintained at two different temperatures.There is no loss of heat across the cylindrical surface and the system is in steady state.Then,find the effective thermal conductivity of the system?
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Soumyabrata Mondal IITJEE 1988383take the resistance of cylinder r1 & cylindrical shell r2.
the resistance are in parallel
1/r=(1/r1)+(1/r2)...............(i)
Let, effective thermal conductivity =K
from the eq. (i)
K(4Ï€R2)L=7(Ï€R2)L+3(3Ï€R2)L [where L is the length of cylinder]
K=4
