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Que. A cylinder of radius r and made of material of thermal conductivity k 1 is surrounded by a cylindrical shell of inner radius r and outer radius 2r. This outer shell is made of a material of thermal conductivity k 2. Net conductivity would be
a. k 1 + 3 k 2/4
b. k 1 + k 2/4
c. k 1 + 3k 2
d. k 1 + k 2
Correct Answer:k 1 + 3 k 2/4
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