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I'm getting stuck on where this additional energy comes to move the piston further outward/inward during adiabatic processes when the only energy changed is during isothermal processes. Can someone care to explain?

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    $\begingroup$ It comes from the internal energy of the gas either decreasing or increasing. $\endgroup$ – Chet Miller Jun 6 '17 at 1:26
  • $\begingroup$ But the heat added to the internal energy is what made the piston move during the isothermal process so how can the change come from internal energy during the adiabatic process change when there is no outside influence during the adiabatic process? $\endgroup$ – mikanim Jun 6 '17 at 7:51
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    $\begingroup$ The internal energy doesn't change during the isothermal process; heat and work are exchanged. In the adiabatic process, no heat is exchanged; work is done and the internal energy changes. $\endgroup$ – Chet Miller Jun 6 '17 at 10:56
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They come from work, i.e. expansion or compression of the gas.

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This question is a duplication. It's already been asked here:

Where does additional heat energy come from in isothermal step of Carnot cycle

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  • $\begingroup$ Hey thanks but no that post discusses isothermal. Mine is focused on adiabatic. $\endgroup$ – mikanim Jun 6 '17 at 7:45
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The most common adiabatic cycle is the internal combustion engine. The energy for this process obviously comes from the combustion of gasoline in each cylinder of the engine. The process can be considered adiabatic because a typical car engine will be operating in the range of 2000-3000 rpm under normal driving conditions, and at these speeds, there is VERY little time for heat transfer to cooling water or the environment during a the four stroke engine cycle.

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