7. Over the years there have been numerous claims about \"perpetual motion machi

Question

7. Over the years there have been numerous claims about "perpetual motion machines" ", ma- chines that will produce useful work with no input of energy. Answer the following questions to the best of your ability, a) (5 pts) Explain why the first law of thermodynamics prohibits the possibility of such a machine existing. b) (5 pts) Another kind of machine, sometimes called a ""perpetual motion of the second kind", operates as follows. Suppose an ocean liner sails by scooping up water from the ocean and then extracting heat from the water, converting the heat to electric power to run the ship, and dumping the water back into the ocean. This process does not violate the first law of thermodynamics, for no energy is created. Energy from the ocean is just converted to electrical energy (thus the energy is conserved). Explain how the second law of thermodynamics prohibits the existence of such a machine.

Explanation / Answer

a)

1st kind --> produces work without energy input

this violates 1st law of thermodynamics which states that energy is conserved and cant be created/destroyed

therefore, if no input, no output

b)

entropy increases in a system, also note that "high" quality heat will be lost to "low quality heat" the reversible process will NOT be possible.

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