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Question
Figure (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.
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Solution
Rods are connected in series, so the rate of flow of heat is same.
Rate of flow of heat is given by
`q = (dQ)/(dt) = "Temperature differences"/ "Thermal resistance"`
As q1 = q2
`⇒ T-0 / (R_{cu}) =(100 - T ) /(R_s)`
`Ak_1 ((T - 0)/(l)) = (100 - T ) 46 `
⇒ 390 T = (100 - T) 46
⇒ T = 10.6° C
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