For the figure shown, when arc $ACD$ and $ADB$ are made of same material, the heat carried between $A$ and $B$ is $H$ . If $ADB$ is replaced with another material, the heat carried becomes $2H$ . If the temperatures at $A$ and $B$ are fixed at $T_1$ and $T_2$ , what is the ratio of the new conductivity to the old one of $ADB$

815-1023

  • A

    $\frac {7}{3}$

  • B

    $2$

  • C

    $\frac {5}{2}$

  • D

    $3$

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