The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity $K$ and $2K$ and thickness $x$ and $4x$ , respectively are $T_2$ and $T_1$ ($T_2$ > $T_1$). The rate of heat transfer through the slab, in a steady state is $\left( {\frac{{A({T_2} - {T_1})K}}{x}} \right)f$, with $f $ which equal to

86-35

  • [AIEEE 2004]
  • [AIIMS 2017]
  • A

    $1$

  • B

    $\frac{1}{2}$

  • C

    $\frac{2}{3}$

  • D

    $\frac{1}{3}$

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