Imagine a piston containing a sample of ideal gas in thermal equilibrium with a large water bath. Assume that the piston head is perfectly free to move unless locked in place, and the walls of the piston readily allow the transfer of energy via heat unless wrapped in insulation. The piston head is unlocked and the gas is in an equilibrium state. For each of the actions described below, state whether the work W done on the gas, the heat energy Q transferred to the gas, and the change in the internal energy ΔEth of the gas are positive (+), negative (-), or zero (0). After each action the piston is reset to its initial equilibrium state. Throughout this item we will assume that the first law of thermodynamics is given by ΔEth=W+Q

Required:
Lock the piston head in place. Hold the piston above a very hot flame. Write down the signs of W, Q, and ΔEth Use +, -, or 0 separated by commas. For example, if Wis positive, Q is negative, and ΔEth is zero, you would type +,-,0.

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

Which notation is used to represent an alpha particle? a. b. c. d.

Which are advantages of renewable resources? check all that apply. renewable energy supplies are completely reliable everywhere. some renewable resources will never be used up. little or no waste is produced by renewable resource plants. electricity can be generated in large quantities. many renewable energy facilities have lower operating costs.