A copper plate of area 0.20 m^2 and thickness 5.0 mm has one face at 100 C and the other at 20 C in steady state. Thermal conductivity of copper k = 400 W/(m K). Find the rate of heat conduction through the plate. Solution: Q/t = k A delta_T / L = (400)(0.20)(100 - 20) / 0.005 = (400)(0.20)(80) / 0.005 = 6400 / 0.005 = 1.28 x 10^6 W. Over a megawatt flows through this small plate - metals conduct enormously well, which is why the same plate in glass (k ~ 1) would pass only about 3200 W.