Question

# Two different metal rods of the same length have their ends kept at the same temperatures θ1 and θ2 with θ2 > θ1. If A1 and A2 are their cross-sectional areas and k1 and k2 their thermal conductivities, the rate of heat flow in the two rods will be same if

A

k1k2=A1A2

B

k1k2=A2A1

C

k1k2=A1θ2A2θ1

D

k1k2=A1θ1A2θ2

Solution

## The correct option is B k1k2=A2A1 Rate of heat flow is Qt=kA(θ2−θ1)l Since (θ2−θ1) and l are the same for the two rods, the rate of flow Qt will be the same if the product kA is the same for the two rods, i.e., if k1A1=k2A2⇒k1k2=A2A1 Hence, the correct choice is (b).

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