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NEET 2017
Exam
NEET
Year
2017
Subject
Physics
Chapter
Thermal Properties of Matter

NEET 2017 · Physics · Thermal Properties of Matter

Two rods A and B of different materials are welded together as...

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K1{K}_{1} and K2{K}_{2}. The thermal conductivity of the composite rod will be

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K _ 1

Options

  1. AK1+K22\dfrac{{K}_{1} + {K}_{2}}{2}
  2. B\dfrac{3\left({K}_{1} + {K}_{2}\right)}{2}
  3. CK1+K2{K}_{1} + {K}_{2}
  4. D2(K1+K2)2\left({K}_{1} + {K}_{2}\right)

Correct answer

A. K1+K22\dfrac{{K}_{1} + {K}_{2}}{2}

Step-by-step solution

Thermal current

H=H1+H2H = {H}_{1} + {H}_{2}

=K1A(T1−T2)d+K2A(T1−T2)d= \dfrac{{K}_{1}A\left({T}_{1} - {T}_{2}\right)}{d} + \dfrac{{K}_{2}A\left({T}_{1} - {T}_{2}\right)}{d}

KEQ2A(T1−T2)d=A(T1−T2)d[K1+K2]\dfrac{{K}_{EQ}2A\left({T}_{1} - {T}_{2}\right)}{d} = \dfrac{A\left({T}_{1} - {T}_{2}\right)}{d}\left[{K}_{1} + {K}_{2}\right]

${K}_{EQ} = \left[\dfrac{{K}_{1} + {K}_{2}}{2}\right]
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