Question

# The ratio of thermal conductivity of two rods of different material is 5 : 4. The two rods of same area of cross-section and same thermal resistance will have the lengths in the ratio4 : 5 9 : 1 1 : 9 5 : 4

Solution

## The correct option is D 5 : 4 Given A1=A2 and K1K2=54  ∵R1=R2∴l1K1A=l2K2A⇒l1l2=K1K2=54 .

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