1) When a computer is turned off, its CPU begins to cool off. Imagine that the internal energy of the CPU is given by U = c1T + c2, where c1 and c2 are constants.
a) Assuming that the whole CPU is at the same temperature (T), and that the convective heat transfer coefficient (h) is constant over the surface area (A) of the CPU. What is the equation for heat loss from the chip? Hint: the chip is the system.
b) Write a first order differential equation that describes the change in the internal energy of the computer chip as a function of h, A, T, and Tsurroudnings. Hint: Write the time dependent form of the 1st law, and use your answer from part a).
c) If h = 200 W/m2•K, A=4 cm2, c = 4 J/K and T8 = 20C, how long does it take for the chip to go from 120C to 100C? Hint: This requires that you solve the differential equation that you just derived.