Researchers have observed that declines in amphibian populations are more pronounced near cities and towns, and especially in habitats associated with waste water treatment facilities. Could high numbers of women taking birth control pills in these densely populated areas really be responsible for frog population declines? In this activity, you will reconstruct the connections underlying the hypothesis that human birth control is causing frog population declines near cities and towns.

Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?