Thermodynamics -- first and second law concepts

In summary, the inventor claims to have invented four engines that operate between constant-temperature reservoirs at 400 and 300 K. Data for each engine, per cycle, can be found in the table. The first and second laws of thermodynamics are discussed and it is determined that engines one and two violate the first law, while engines three and four violate the second law. The conversation also mentions calculating entropy changes for the reservoirs and relates it to the efficiency, which should not be greater than 40%.
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Homework Statement


An inventor claims to have invented four engines, each of which operates between constant-temperature reservoirs at 400 and 300 K. Data on each engine, per cycle of operation, can be found in the table below. Of the first and second laws of thermodynamics, which (if either) does each engine violate?
Engine |||||||||| 1 ||||||||||| 2 |||||||||| 3 |||||||||| 4
QH |||||||||||| 200J ||||| 500J||||||| 600J ||||| 100J
QL||||||||||||| -175J||||| -200J|||||| -200J|||||| -90J
W |||||||||||||||40J ||||||||400J ||||||||400J|||||||10J
Of the first and second laws of thermodynamics, which (if either) does each engine violate?

Homework Equations


should i use the efficiency rule? I know that first law says that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed. then Qh=|Qc|+W then one and two violates first law since in both Qh<|Qc|+W But how can i show that three and four violates the second law?
 
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  • #2
Calculate the entropy changes for the reservoirs in cases 3 and 4.
 
  • #3
Chestermiller said:
Calculate the entropy changes for the reservoirs in cases 3 and 4.
Yeah, Thanks I didn't pay attention to that at the beginning
also we could relate it to the efficiency for which it must not be greater than 40% (carnot engine)
 

What is the first law of thermodynamics?

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, but can only be transferred or converted from one form to another.

What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This means that energy tends to disperse and become less organized, leading to a decrease in available energy for useful work.

What is the difference between heat and temperature?

Heat is the transfer of thermal energy from one object to another, while temperature is a measure of the average kinetic energy of the particles in a substance. In other words, heat is a form of energy, while temperature is a measure of the intensity of heat.

How is the first law of thermodynamics applied in everyday life?

The first law of thermodynamics is applied in various aspects of our daily lives, such as in cooking, heating and cooling systems, and transportation. It helps us understand how energy is conserved and transferred in different processes.

What is an example of the second law of thermodynamics in action?

An example of the second law of thermodynamics is the process of heat transfer from a hot object to a cold object. The heat will always flow from the hotter object to the colder object, until both objects reach the same temperature, and the energy is evenly distributed.

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