Question

pls answer this question.
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Answer 1

[A]

In configuration 1

total thermal resistance Req=

ℓKA+ℓ2KA=32ℓKA

In configuration 2

R'eq=(1×121+12)ℓKA=13ℓKA

We have

Q=(T1−T2)Rt

t ∝R

t2t1=R2R1⇒t2=29×9=2 sec