First Law for a Thermodynamic Cycle

This phase diagram shows that the process path for a cycle begins and ends at the same state.
Since the initial and final states are identical in a thermodynamic cycle, the system experiences no net change in state. Therefore, the system also experiences no net change in energy for the cycle.
Sign convention arrow for work.
Sign convention arrow for heat.
Generic system boundary.
The change in the total energy of the system after the cycle is zero.
OR :
In words, the

first law of thermodynamics

or the

conservation of energy principle

applied to a


Net Energy Transferred by
Heat for the Cycle
Net Energy Transferred by Work for the Cycle
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Ch 4, Lesson F, Page 2 - First Law for a Thermodynamic Cycle