1. When the heat flow through unit area of a sheet of insulating material of thickness 3.0mm is 8.0kWm^-2, the temperature drop across the sheet is 100K. Calculate the thermal conductivity of the material.

2. A cylindrical rod of cross-sectional area 5.0mm² is made by joining a 0.30m rod of silver to a 0.12m rod of nickel. The silver end is maintained at 290K and the nickel end at 440K. given the thermal conductivities of silver and nickel are 0.42kWm^-1K^-1 and 91Wm^-1K^-1 respectively, calculate:

1. the temperature of the join under steady conditions, and

3. What length of copper rod of the same diameter as the composite rod in question 2 would have the same effect on the the rate of heat flow ? The conductivity of copper is 0.39kWm^-1K^-1

4. The temperature of a room is maintained at 292K when the outdoor temperature is 274K. the glass windows in the room have a total area of 6.0m² and a uniform thickness of 4.0mm. use this information to calculate the power required to maintain this temperature difference assuming that the only heat loss is through the glass which has thermal conductivity 0.80Wm^-1K^-1. Why is this answer unrealistically large

5. A cylindrical poker of total length 0.60m is made of an iron cylinder, length 0.50m and thermal conductivity 0.80Wcm^-1K^-1 attached to a wooden handle (thermal conductivity 0.40Wm^-1K^-1) of length 0.10m with the same diameter of 5mm. If the poker is held by hand (at 37^oC) in a fire of temperature 1000^oC, what is the rate of heat flow along the poker ?

Sketch a graph to show the temperature gradient a long this poker.

1. What is the difference between the two methods ?
2. Why is it impractical to have a single method for any one solid material?

1) 0.24Wm^-1K^-1  2a) 343K b)0.37W 3) 0.79m 4) 22kW 5) 0.076W 7) 12W