Two conductors are made of the same material and have the same length. conductor a is a solid wire of diameter 0.79 mm. conductor b is a hollow tube of outside diameter 1.4 mm and inside diameter 0.91 mm. what is the resistance ratio ra/rb, measured between their ends?

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.