An aluminium rod and a copper rod of equal length 1.0 m and cross-sectional area 1 cm2 are welded together as shown in the figure . One end is kept at a temperature of 20°C and the other at 60°C. Calculate the amount of heat taken out per second from the hot end. Thermal conductivity of aluminium = 200 W m−1°C−1 and of copper = 390 W m−1°C−1.
q1 and q2 are heat currents. In other words, they are the rates of flow of heat through aluminium and copper rod, respectively.
Applying KVL at the hot junction, we get
q = q1 + q2
Rate of heat flow, `q = (KA Delta T)/ l`
As q = q1 + q2
`(K_pA(T_1 + T_2))/l = (k_1A(T_1 - T_2))/l +(KA Delta T)/ l`
Kp =K1 + k2
= 390 + 200 = 590 W/m°C
`⇒ q = (K_PA( T_1 _ T_2))/l`
q= 2.36 W