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# Thermodynamics Question 2

When a gas expands adiabatically; it does work on its surroundings. But if there is no heat input to the gas, where does the energy come from to do the work?

Note by Mark Kevin Aguilar
4 years, 5 months ago

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It's the internal energy of the gas that it uses to do work in an adiabatic process.

- 4 years, 5 months ago

yeah that's right.......and that's why the temperature of the gas drops after adiabatic expansion as temperature is directly proportional to internal energy of the gas.........

- 4 years, 5 months ago

u r correct but at inversion temp the opp happens

- 4 years, 5 months ago

You are back!!. Was the pendulum (changing value of g) question correct?

- 4 years, 5 months ago

yeah that's it.............

- 4 years, 5 months ago

It is due to intramolecular force existing between molecules by 'String Theory' or 'Harmonic Oscillator'!!

- 4 years, 5 months ago

from internal energy as dQ=dU+dW and dQ is 0

- 4 years, 5 months ago

If gas expands adiabatically and if it is a free expansion no work is done by the gas....free expansion means into vaccum..since question is not that clear, will answer another question also...if it expands against a piston, definitely it has to do some work and it reduces its temperature hence uses itS internal energy...

- 7 months, 3 weeks ago

Internal pressure of gas is more than external pressure , so gas expands without any heat input.

- 2 years ago

internal energy

- 4 years, 5 months ago