Six wire each of cross-sectional area $A$ and length $l$ are combined as shown in the figure. The thermal conductivities of copper and iron are $K_1$ and $K_2$ respectively. The equivalent thermal resistance between points $A$ and $C$ is :-
Six wire each of cross-sectional area $A$ and length $l$ are combined as shown in the figure. The thermal conductivities of copper and iron are $K_1$ and $K_2$ respectively. The equivalent thermal resistance between points $A$ and $C$ is :-
- A
$\frac{l(K_1+K_2)}{K_1K_2A}$
- B
$\frac{2l(K_1+K_2)}{K_1K_2A}$
- C
$\frac{l}{(K_1+K_2)A}$
- D
$\frac{2l}{(K_1+K_2)A}$
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