MCQ
Two rectangular blocks, having indentical dimensions, can be arranged either in configuration $I$ or in configuration $II$ as shown in the figure, On of the blocks has thermal conductivity $k$ and the other $2 \ k$. The temperature difference between the ends along the $x$-axis is the same in both the configurations. It takes $9\ s$ to transport a certain amount of heat from the hot end to the cold end in the configuration $I$. The time to transport the same amount of heat in the configuration $II$ is :
  • $2.0 \ s$
  • B
    $3.0 \ s$
  • C
    $4.5 \ s$
  • D
    $6.0 \ s$

Answer

Correct option: A.
$2.0 \ s$
a
In configuration $1$ equivalent thermal resistance is $\frac{3 R}{2}$

In configuration $2$ equivalent thermal resistance is $\frac{R}{3}$ Thermal Resistance $\propto$ time taken by heat flow from high temperature to low temperature

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