Two rectangular blocks, having identical dimensions, an be arranged either in configuration-I or in configuration-II as shown in the figure. One of the blocks has thermal conductivity k and the other 2k. The temperature difference between the ends along the x-axis is the same in both the configurations. It takes 9s 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

Options

A. `2.0 s`
B. `3.0s`
C. `4.5 s`
D. `6.0s`

Answer

A

Explanation

In configuration `1` equivalent thermal resistance is `(3R)/(2)`
In configuration `2` equivalent thermal resistance is `(R )/(3)`
Thermal Resistance `prop` time taken by heat flow from high temperature to low temperature