hree rods of same dimensions are arranged as shown in figure they have thermal conductivities ${K_1},{K_2}$ and${K_3}$ The points $P$ and $Q$ are maintained at different temperatures for the heat to flow at the same rate along $PRQ$ and $PQ$ then which of the following option is correct

86-18

  • A

    ${K_3} = \frac{1}{2}({K_1} + {K_2})$

  • B

    ${K_3} = {K_1} + {K_2}$

  • C

    ${K_3} = \frac{{{K_1}{K_2}}}{{{K_1} + {K_2}}}$

  • D

    ${K_3} = 2({K_1} + {K_2})$

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