Physics-
General
Easy

Question

Three rods of the same dimension have thermal conductivities 3K, 2K and K. They are arranged as shown in fig. Given below, with their ends at 100oC, 50oC and 20oC. The temperature of their junction is

  1. 6 0 to the power of o end exponentC    
  2. 7 0 to the power of o end exponent C    
  3. 50o C    
  4. 35o C    

The correct answer is: 7 0 to the power of o end exponent C


    Let the temperature of junction be q then according to following figure.

    H = H1 + H2
    Þ fraction numerator 3 K cross times A cross times left parenthesis 100 minus theta right parenthesis over denominator l end fraction equals fraction numerator 2 K A left parenthesis theta minus 50 right parenthesis over denominator l end fraction plus fraction numerator K A left parenthesis theta minus 20 right parenthesis over denominator l end fraction
    Þ 300 – 3q = 3q – 120 Þ q = 70°C

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