Question

Please help

13. If you have a closed loop on a PV diagram, the work done is: 14. Define reversible process 15. State the Second Law of Thermodynamics, both the first and second versions 16. Give an everyday example of the Second Law of Thermodynamics

Answer 1

1
The net work involved is the enclosed area on the P-V diagram. If the cycle goes clockwise, the system does work. A cyclic process is the underlying principle for an engine.
If the cycle goes counterclockwise, work is done on the system every cycle. An example of such a system is a refrigerator or air conditioner.
Because the process is cyclic, there is no change in internal energy after each cycle. Therefore the net work done in each cycle equals the heat added to the system.

2
The process in which the system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamics properties of the universe is called a reversible process. In the figure below, let us suppose that the system has undergone a change from state A to state B. If the system can be restored from state B to state A, and there is no change in the universe, then the process is said to be a reversible process. The reversible process can be reversed completely and there is no trace left to show that the system had undergone thermodynamic change.

3
The Second Law of Thermodynamics states that the state of entropy of the entire universe, as an isolated system, will always increase over time. The second law also states that the changes in the entropy in the universe can never be negative.

4
For example, someone might put an ice cube into a glass of warm lemonade and then forget to drink the beverage. An hour or two later, they will notice that the ice has melted but the temperature of the lemonade has cooled. This is because the total amount of heat in the system has remained the same, but has just gravitated towards equilibrium, where both the former ice cube (now water) and the lemonade are the same temperature. This is, of course, not a completely closed system. The lemonade will eventually become warm again, as heat from the environment is transferred to the glass and its contents.