(a) Over the years there have been numerous claims about "perpetual motion machines," machines that will produce useful work with no input of energy. Explain why the first law of thermodynamics prohibits the possibility of such a machine existing. (b) 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. Show that the second law of thermodynamics prohibits the existence of such a machine.

Step by step solution

01

Understanding the first law of thermodynamics

The first law of thermodynamics states that energy cannot be created or destroyed in an isolated system. It can only change from one form to another. Thus, a machine that produces useful work with no input of energy, also known as a perpetual motion machine of the first kind, violates this law because it implies that energy is being created.

02

Understanding the second law of thermodynamics

The second law of thermodynamics says that the entropy of any isolated system always increases. A machine that operates by extracting heat from the ocean water, transforming it into electricity for the running of the ship and returning the water back to the ocean suggests a decrease in the overall entropy. This would be in contradiction with the second law of thermodynamics. Converting heat from one body to do work entirely and without losses, assumes a 100 % efficient heat engine which is impossible as it always results in some energy wasted as heat to the surroundings or a part of energy that's unavailable for work.

03

Concluding the impossibility of both machines

As per the laws of thermodynamics, both perpetual motion machines of the first and second kind are not possible. The first law asserts the impossibility of creating energy from nowhere, which overrules the existence of the first kind. The second law, on the other hand, disproves the idea of the existence of a machine that could work with 100 % efficiency, converting all heat energy into usable work without any losses.

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