What is the difference between isothermal and adiabatic expansion in terms of change in heat, change in internal energy, work done, change in volume, pressure, and temperature.
Dear student,
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Heat: Adiabatic expansion is an increase in volume while pressure is maintained constant. When this occurs, temperature also increases .
Isothermal expansion is an increase in volume while temperature is maintained constant. When this occurs, pressure decreases. - change in internal energy: In adiabatic process, internal energy reduces, Isothermal process, internal energy remains constant.
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work done: Adiabatic expansion of compressed air produces much less work than isothermal expansion starting from the same conditions
The work done during an adiabatic process is given by,
W = C(v){T1 – T2)
In isothermal process, W= p0(fvV0-V0)
Suppose that the temperature of an ideal gas is held constant by keeping the gas in thermal contact with a heat reservoir. If the gas is allowed to expand quasi-statically under these so called isothermal conditions then the ideal equation of state tells us that
This is usually called the isothermal gas law .
Suppose, now, that the gas is thermally isolated from its surroundings. If the gas is allowed to expand quasi-statically under these so called adiabatic conditions then it does work on its environment, and, hence, its internal energy is reduced, and its temperature changes.
Isothermal Process | Adiabatic Process | |
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1. | In an isothermal process, temperature of the system remains constant. | In an adiabatic process, temperature of the system changes. |
2. | In this process, the system exchanges heat with the surroundings. | In this process, the system does not exchange heat with the surroundings. |
3. | Total internal energy of the system remains constant (DE = 0). | Total internal energy DE of the system changes. |
4. | Total heat content of the system changes (DH � 0). | Total heat content of the system remains constant (DH = 0). |
5. | In this process, the system is not thermally isolated. | In this process, the system is thermally isolated. |
6. | This process can be made reversible. | This process cannot be made reversible. |
7. | In this process, Q = W as DE = 0. | In this process, W = (-) DE as DQ = 0 |