Thermodynamics An Engineering Approach kau（热力学考一个工程方法）.pdf

Thermo 1 (MEP 261) Thermodynamics An Engineering Approach Yunus A. Cengel Michael A. Boles 7th Edition, McGraw-Hill Companies, ISBN-978-0-07-352932-5, 2008 Sheet 2:Chapter 2 2-4C The sum of all forms of the energy a system possesses is called total energy. In the absence of magnetic, electrical, and surface tension effects, the total energy of a system consists of the kinetic, potential, and internal energies. Solution 2-15C Energy can cross the boundaries of a closed system in two forms: heat and work. 2-20C It is a heat interaction since it is due to the temperature difference between the sun and the room. 2-22C Point functions depend on the state only whereas the path functions depend on the path followed during a process. Properties of substances are point functions, heat and work are path functions. 2-24C The work done is the same, but the power is different. 2-28 A linear spring is elongated by 20 cm from its rest position. The work done is to Solution be determined. Analysis The spring work can be determined from Solution Solution 2-34C Warmer. Because energy is added to the room air in the form of electrical work. Solution 2-35C Energy can be transferred to or from a control volume as heat, various forms of work, and by mass transport. Solution Solution Solution