NEET-XII-Physics
28: Heat Transfer
- #23Figure (28-E2) shows a copper rod joined to a steel rod. The rods have equal length and equal cross sectional area. The free end of the copper rod is kept at 0°C and that of the steel rod is kept at 100°C. Find the temperature at the junction of the rods. Conductivity of copper = 390 W m-1°C-1 and that if steel = 46 W m-1°C-1.
Figure
Ans :
Rods are connected in series, so the rate of flow of heat is same.
q1 = q2
Rate of flow of heat is given by
`` q=\frac{dQ}{dt}=\frac{\,\mathrm{\,Temperature\,}\,\mathrm{\,difference\,}}{\,\mathrm{\,Thermal\,}\,\mathrm{\,resistance\,}}``
As q1 = q2,
`` \Rightarrow \frac{T-0}{{R}_{\,\mathrm{\,cu\,}}}=\frac{100-T}{{R}_{\,\mathrm{\,S\,}}}``
`` A{K}_{1}\left(\frac{T-0}{l}\right)=\left(\frac{100-T}{l}\right){K}_{2}A``
`` \Rightarrow 390\,\mathrm{\,T\,}=\left(100-\,\mathrm{\,T\,}\right)46``
`` \Rightarrow \,\mathrm{\,T\,}=10.6°\,\mathrm{\,C\,}``
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