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ChatGPT
more than 1 week ago
The adiabatic index, also known as the ratio of specific heats, is defined as:
γ = Cp/Cv
Where:
- Cp is the specific heat at constant pressure
- Cv is the specific heat at constant volume
To prove that adiabatic = Cp/Cv, we can start with the definition of the adiabatic process, which is a thermodynamic process in which no heat is exchanged with the surroundings. In an adiabatic process, the change in internal energy (ΔU) is equal to the work done on the system (W), as there is no heat transfer:
ΔU = W
Using the first law of thermodynamics, we have:
ΔU = Q - W
Since Q = 0 for an adiabatic process, we have:
ΔU = -W
For an ideal gas, the change in internal energy can be expressed as:
ΔU = nCvΔT
Where:
- n is the number of moles of gas
- Cv is the specific heat at constant volume
- ΔT is the change in temperature
Substituting this expression into the equation for the change in internal energy, we get:
nCvΔT = -W
The work done on the gas can be expressed as:
W = PΔV
Where:
- P is the pressure
- ΔV is the change in volume
For an ideal gas, the ideal gas law states that:
PV = nRT
Where:
- R is the gas constant
- T is the temperature
Differentiating the ideal gas law with respect to volume, we get:
PΔV = nRΔT
Substituting this expression for work into the equation for the change in internal energy, we have:
nCvΔT = -nRΔT
Dividing both sides by nΔT, we get:
Cv = -R
Similarly, we can show that:
Cp = R
Therefore, the ratio of specific heats, γ, is equal to:
γ = Cp/Cv = R/R = 1
Hence, we have proved that adiabatic = Cp/Cv = 1.
γ = Cp/Cv
Where:
- Cp is the specific heat at constant pressure
- Cv is the specific heat at constant volume
To prove that adiabatic = Cp/Cv, we can start with the definition of the adiabatic process, which is a thermodynamic process in which no heat is exchanged with the surroundings. In an adiabatic process, the change in internal energy (ΔU) is equal to the work done on the system (W), as there is no heat transfer:
ΔU = W
Using the first law of thermodynamics, we have:
ΔU = Q - W
Since Q = 0 for an adiabatic process, we have:
ΔU = -W
For an ideal gas, the change in internal energy can be expressed as:
ΔU = nCvΔT
Where:
- n is the number of moles of gas
- Cv is the specific heat at constant volume
- ΔT is the change in temperature
Substituting this expression into the equation for the change in internal energy, we get:
nCvΔT = -W
The work done on the gas can be expressed as:
W = PΔV
Where:
- P is the pressure
- ΔV is the change in volume
For an ideal gas, the ideal gas law states that:
PV = nRT
Where:
- R is the gas constant
- T is the temperature
Differentiating the ideal gas law with respect to volume, we get:
PΔV = nRΔT
Substituting this expression for work into the equation for the change in internal energy, we have:
nCvΔT = -nRΔT
Dividing both sides by nΔT, we get:
Cv = -R
Similarly, we can show that:
Cp = R
Therefore, the ratio of specific heats, γ, is equal to:
γ = Cp/Cv = R/R = 1
Hence, we have proved that adiabatic = Cp/Cv = 1.
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Google Gemini AI
more than 1 week ago
Adiabatic Process:
An adiabatic process is a thermodynamic process in which there is no heat transfer between the system and its surroundings.
Specific Heats:
- Specific heat at constant pressure (Cp): The heat capacity of a substance that is allowed to change volume while being heated.
- Specific heat at constant volume (Cv): The heat capacity of a substance that is constrained to a constant volume while being heated.
Proof:
For an adiabatic process, the first law of thermodynamics states that:
```
dU = dQ - dW
```
where:
- dU is the change in internal energy
- dQ is the heat added to the system
- dW is the work done by the system
Since an adiabatic process involves no heat transfer, dQ = 0. Therefore, the equation becomes:
```
dU = -dW
```
The change in internal energy can be expressed as:
```
dU = Cp - dT
```
where dT is the change in temperature.
The work done by the system can be expressed as:
```
dW = -P - dV
```
where P is the pressure and dV is the change in volume.
Combining the above equations, we get:
```
Cp - dT = -P - dV
```
For an ideal gas, the relationship between pressure, volume, and temperature is given by the ideal gas law:
```
PV = nRT
```
where:
- n is the number of moles
- R is the ideal gas constant
Differentiating the ideal gas law with respect to volume gives:
```
P - dV + V - dP = nR - dT
```
Substituting this equation into the previous equation, we get:
```
Cp - dT = -(P - dV + V - dP)
```
Simplifying the equation, we get:
```
Cp - dT = -P - dV - V - dP
```
Comparing this equation to the definition of Cv, we get:
```
Cp = Cv + V - dP/dV
```
For an isothermal process (constant temperature), dT = 0. Therefore:
```
Cp = Cv
```
Hence, for an adiabatic process, the specific heat at constant pressure (Cp) is equal to the specific heat at constant volume (Cv).
An adiabatic process is a thermodynamic process in which there is no heat transfer between the system and its surroundings.
Specific Heats:
- Specific heat at constant pressure (Cp): The heat capacity of a substance that is allowed to change volume while being heated.
- Specific heat at constant volume (Cv): The heat capacity of a substance that is constrained to a constant volume while being heated.
Proof:
For an adiabatic process, the first law of thermodynamics states that:
```
dU = dQ - dW
```
where:
- dU is the change in internal energy
- dQ is the heat added to the system
- dW is the work done by the system
Since an adiabatic process involves no heat transfer, dQ = 0. Therefore, the equation becomes:
```
dU = -dW
```
The change in internal energy can be expressed as:
```
dU = Cp - dT
```
where dT is the change in temperature.
The work done by the system can be expressed as:
```
dW = -P - dV
```
where P is the pressure and dV is the change in volume.
Combining the above equations, we get:
```
Cp - dT = -P - dV
```
For an ideal gas, the relationship between pressure, volume, and temperature is given by the ideal gas law:
```
PV = nRT
```
where:
- n is the number of moles
- R is the ideal gas constant
Differentiating the ideal gas law with respect to volume gives:
```
P - dV + V - dP = nR - dT
```
Substituting this equation into the previous equation, we get:
```
Cp - dT = -(P - dV + V - dP)
```
Simplifying the equation, we get:
```
Cp - dT = -P - dV - V - dP
```
Comparing this equation to the definition of Cv, we get:
```
Cp = Cv + V - dP/dV
```
For an isothermal process (constant temperature), dT = 0. Therefore:
```
Cp = Cv
```
Hence, for an adiabatic process, the specific heat at constant pressure (Cp) is equal to the specific heat at constant volume (Cv).
0
