Can someone explain this thermodynamics related doubt i have?

In summary: In scenario one, heat is suddenly added causing a temperature and pressure increase, but the volume remains constant. This implies that q (heat) equals n (number of moles) multiplied by Cv (specific heat at constant volume) multiplied by dT (change in temperature). In addition, when the pressure is decreased adiabatically to initial pressure p1, there will be adiabatic work done in expanding to lower pressure, at the cost of internal energy. In scenario two, heat is added at a constant pressure p1, causing expansion and a change in internal energy. The question then asks if the two
  • #1
lawofnature
2
1
Assume a piston cylinder arrangement. External pressure always equals internal pressure ( reversible conditions ). Now consider these two scenarios:

Scenario one: q heat is suddenly added to the arrangement causing a temperature rise and consequently pressure rise, but the volume is yet constant. That implies:
q = n Cv dT
Now let's decrease the pressure adiabatically to initial pressure p1 (before temp. rise). There will be adiabatic work done in expanding to lower pressure at the cost of internal energy:
p dV = n Cv dT

Scenario two: q heat is added at a constant pressure p1 (isobaric process) causing expansion and change in internal energy.

Are the two scenarios equivalent in terms of change in internal energy, work done and final expansion (of volume)?
 
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  • #2
lawofnature said:
Assume a piston cylinder arrangement. External pressure always equals internal pressure ( reversible conditions ). Now consider these two scenarios:

Scenario one: q heat is suddenly added to the arrangement causing a temperature rise and consequently pressure rise, but the volume is yet constant. That implies:
q = n Cv dT
Now let's decrease the pressure adiabatically to initial pressure p1 (before temp. rise). There will be adiabatic work done in expanding to lower pressure at the cost of internal energy:
p dV = n Cv dT

Scenario two: q heat is added at a constant pressure p1 (isobaric process) causing expansion and change in internal energy.

Are the two scenarios equivalent in terms of change in internal energy, work done and final expansion (of volume)?
Why don't you just run the calculations as see for yourself what happens (rather than guessing)?

Chet
 

1. What is thermodynamics?

Thermodynamics is the branch of physics that deals with the relationship between heat and other forms of energy. It studies the behavior of systems and how they change in response to energy transfer.

2. How does thermodynamics relate to everyday life?

Thermodynamics is present in many aspects of our daily lives, such as cooking, transportation, and electricity generation. It helps us understand how energy is converted and utilized in various processes.

3. 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, only transferred or converted from one form to another.

4. Can you explain entropy in simple terms?

Entropy is a measure of the disorder or randomness in a system. It tends to increase over time, meaning that systems naturally move towards a state of higher disorder or randomness.

5. How does the second law of thermodynamics relate to entropy?

The second law of thermodynamics states that the total entropy of an isolated system always increases over time. This means that in any process, the overall disorder or randomness of the system will increase, and no process can be 100% efficient.

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