Sun February 13, 2011 By: Vishnu K

If the movement of a car from one place and back to the same place can be considered as a cyclic process the total internal energy change of the system is not zero. How can it be so?

Expert Reply
Mon February 14, 2011
Dear student,
When a system returns to its original state after completing a series of changes, then it is known that a cycle is completed. This process is known as cyclic process. In a cyclic process the initial and the final state is same. As the internal energy U of the system depends only on the state of the system so in a cyclic process the net change of internal energy ∆U will be equal to zero i.e. ∆U = 0. Hence from the first law:

∆U = 0 = q + w
Hence, q = – w

Hope this helps.


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