JEE Main & Advanced Physics Transmission of Heat Question Bank Topic Test - Transmission of Heat (3-5-21)

  • question_answer
    Two rods having thermal conductivity in the ratio of 5 : 3 having equal lengths and equal cross-sectional area are joined by face to face. If the temperature of the free end of the first rod is \[100{}^\circ C\] and free end of the second rod is \[{{20}^{o}}C\]. Then temperature of the junction is

    A) \[70{}^\circ C\]

    B) \[50{}^\circ C\]

    C) \[50{}^\circ C\]

    D) \[90{}^\circ C\]

    Correct Answer: A

    Solution :

    Temperature of interface \[\theta =\frac{{{K}_{1}}{{\theta }_{1}}+{{K}_{2}}{{\theta }_{2}}}{{{K}_{1}}+{{K}_{2}}}\]
    It is given that \[\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{5}{3}\] \[\Rightarrow \] \[{{K}_{1}}=5K\] and \[{{K}_{2}}=3K\]
    \[\theta =\frac{5K\times 100+3K\times 20}{5K+3K}\]\[=\frac{560K}{8K}\]\[=70{}^\circ C\]

You need to login to perform this action.
You will be redirected in 3 sec spinner