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 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 Wm–1 °C–1 and of copper = 390 Wm–1 °C–1.
Given
Area of cross section
A =1 cm2
=1×10–4 m2
Thermal conductivity of aluminium, KAl = 200 W/m°C
copper, KCu = 390 W/m°C
Now since these rods are connected in parallel,
So heat flowing per second
= qAl + qCu
= KAl ×A× ∆T + KCu ×A× ∆T
= KAl A × (60-20) + KCu A × (60-20)
= 1×10–4 m2 × 40 (200+ 390)
= 2.36 W
Heat drawn in 1 second = 2.36 W