Three building materials, plasterboard, brick, and wood, all the same thickness and area, are sandwiched to form a wall. Temperatures are 27 degrees Celsius at the inside plasterboard surface and 0 degrees celsius at the outside wood surface. Find the temperature where the plasterboard meets the brick and where the brick meets the wood.k for plasterboard = .40k for brick = .70k for wood = .2
1/0.4+1/0.7+1/.2 = 7.5+1/.7 or about 8.93 the plasterboard drops 27*2.5/8.93 C : about 7.7C so temperature at plasterboard/brick is around 19.3 C the wood drops twice as much about 15.2C so brick-wood interface is around 15.2C. Appropriate numerical precision when the conductivities are given to 2 significant figures means your answers should be about 19C and 15C. The brick is awful! Have a look at the link below; even thermal grease isn't much worse than this brick but the values do seem to be pretty typical.
