The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m K and 0.020 W/m K, respectively, while other tissues inside the body have conductivities of about 0.50 W/m K. Assume that between the core region of the body and the skin sin face lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. (b) Find the rate of energy loss when the core temperature is 37C and the exterior temperature is 0C. Assume that both a protective layer of clothing and an insulating layer of unmoving air a absent, and a body area of 2.0 m2.

The Surface temperature of the Sun is about 5750 K. What is this temperature on the Fahrenheit scale?

A large body of lava from a volcano has stopped flowing and is slowly cooling. The interior of the lava is at 1200C, its surface is at 450C, and the surroundings are at 27.0C. (a) Calculate the rate at which energy is transferred by radiation from 1.00m2 of surface lava into the surroundings, assuming the emissivity is 1.00. (b) Suppose heat conduction to the surface occurs at the same rate. What is the thickness of the lava between the 450C surface and the 1200C interior, assuming that the lava’s conductivity is the same as that of brick?