Definitions of Heat and Work

Definitions of Heat and Work - The addition of work,...

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Definitions of Heat and Work Both heat and work have intuitive definitions. However, we need to forego those as we study thermodynamics, because they can be misleading if not used carefully. To that end, we will rigorously define both concepts here. Heat is the transfer of energy to a system via thermal contact with a reservoir. Work is the transfer of energy to a system via a change in the parameters of the system, such as volume. This seemingly small distinction has significant consequences. Remember that a transfer of energy from a reservoir must obey the thermodynamic identity (taken for constant N and V), dU = τ . Therefore a change in energy, i.e. a heat transfer, is accompanied by an entropy transfer.
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Unformatted text preview: The addition of work, however, can't change the entropy of the system since we are only changing the external environment of the system. We can look at the thermodynamic identity in a new way. The first term, d , can be thought of as the heat input, written dQ . The second term, - p dV , can be thought of as the work input, written dW . The third term, dN , can be thought of as the chemical work input, written dW c . Therefore the total change in energy is due entirely to the sum of the heat inputted, work, and chemical work done on the system....
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This note was uploaded on 02/09/2012 for the course PHY PHY2053 taught by Professor Davidjudd during the Fall '10 term at Broward College.

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