McGraw-Hill's SAT Subject Test Physics by Christine Caputo

Author:Christine Caputo [Caputo, Christine]
Language: eng
Format: epub
Tags: Study Guides, Study Aids, Sat
ISBN: 9780071762953
Google: 4N99ubj_4GMC
Amazon: 0071762949
Publisher: McGraw-Hill
Published: 2012-03-18T19:00:00+00:00

Special Thermodynamic Processes

The first law of thermodynamics explains that a system’s internal energy can be changed by the transfer of energy either as heat, work, or some combination of the two. Several processes are special conditions of the first law.

Adiabatic A process is said to be adiabatic if it is thermally insulated from its environment. In other words, no energy is transferred as heat. If a change is adiabatic, , so . Consider a gas in a cylinder confined by a piston. The temperature of the gas will change as the internal energy changes. Therefore, the gas will warm up as the gas is compressed and cool down as the gas expands. Adiabatic processes are considered theoretically only because perfect thermal insulation does not exist. For compression or expansion that occurs rapidly, however, the process approaches adiabatic conditions because heat takes time to flow.

Isothermal In an isothermal process, the internal energy remains constant, and there is no change in temperature. As a result, , so . The heat flow and the work done exactly balance each other. Any energy added to a system as heat is removed as work done by the system. Any energy added to the system by work done on it is removed as heat.

Isovolumetric No work is done in an isovolumetric process. As a result, , so . Any energy added to the system as heat increases the internal energy. Any energy removed from the system as heat decreases the internal energy.

Isolated System A system is said to be isolated if it experiences no heat or work interactions with the surrounding environment. There is no change in the internal energy for a closed system.

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