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Unformatted text preview: Phys 122 – College physics Midterm 2 Review ! II. Thermodynamics C. Laws of Thermodynamics 1. Systems, states, and processes a. System : quantity of matter enclosed by boundaries or surfaces (real or imaginary; described using macroscopic properties ( T , p , V ) Heat reservoir : a large separate system with unlimited heat capacity; the heat entering or leaving a system comes from or goes to a heat reservoir b. State : specific combination of variables ( T , p , V ) Equation of state : an equation relating the state variables; describes the system c. Process : a change in the system or state variables (heating/cooling) 2. Zeroth Law : Given three objects at temperature T 1 , T 2 , and T 3 , if T 1 = T 2 and T 2 = T 3 , then T 1 = T 3 . 3. First Law : states conservation of energy W U Q + ∆ = ‼ Be careful here with the signs. If heat enters the system, the temperature increases, hence ∆ U is positive. If the system does work, W is positive. If heat leaves the system, the temperature decreases, so ∆ U is negative. If work is done on the system, W is negative. ‼ The work done equals the area under the curve in a pV diagram. 4. Processes for an ideal gas ↓ a. Isothermal process : process happens at constant temperature; therefore, ∆ U = 0. From the first law, we then have Q = W . In a pV diagram: Work in an isothermal process is given by = 1 2 ln V V nRT W isotherm . b. Isobaric process : process occurs at constant pressure In a pV diagram: ! Note that the last page contains a list of symbols used and what they mean. Only the equations and constants will be given on the midterm. ↓ Please refer to the handout on Thermodynamic Processes. M. Ouellette, 9 November 2006 Page 1 of 6 p V 1 2 Work in an isobaric process is given by V p W ∆ = isobaric . c. Isometric process : process takes place at a constant volume: ∆ V = 0; therefore, from the first law we have Q = ∆ U . In a pV diagram: No work is done in an isometric process since there is no area under the curve....
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This test prep was uploaded on 04/09/2008 for the course PHYS 122 taught by Professor Ouelette during the Fall '07 term at Cal Poly.
- Fall '07