## In This post you will get answer of Q.

Two rectangular blocks , having indentical dimensions , can br 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 2 K.The temperature difference between the ends along the x-axis is the same in both the configuration. 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

Solution:

## $R_1 =R_1 +R_2 =bigg(frac{1}{KA}bigg)+bigg(frac{1}{2KA}bigg)=frac{3}{2}bigg(frac{1}{KA}bigg)$

$frac{1}{R_{II}}=frac{1}{R_1}+frac{1}{R_2}=frac{KA}{l}+frac{2KA}{l}$

or $R_{II}=frac{1}{3KA}=frac{R_1}{4.5}$

Since thermal resistance $R_{II}$ is 4.5 times less than thermal resistance R$_I$

$therefore , , , , , , , t_{II}=frac{t_{I}}{4.5}=frac{9}{4.5}=2s$