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Chapter 18: Thermodynamics
Terms in this set (16)
(33) Show that the ideal efficiency is 90% for an engine in which fuel is heated to 3000 K and the surrounding air is 300 K.
(35) What is the ideal efficiency of an automobile engine that operates between the temperatures 600°C and 320°C? (Why is your answer not 47%?)
(45) When heat flows from a warm object in contact with a cool object, do both objects undergo the same amount of temperature change?
(57) How does the ideal efficiency of an automobile related to the temperature of the engine and the temperature of the environment in which it operates? Be specific.
(61) Could you cool a kitchen by leaving the refrigerator door open and closing the kitchen door and windows? Explain.
(65) A refrigerator moves heat from cold to warm. Why doesn't this violate the second law of thermodynamics?
the study of heat and its transformation into different forms of energy
the lowest possible temperature that a substance can have; the temperature at which particles of a substance have their minimum kinetic energy
the total energy (kinetic plus potential) of the submicroscopic particles that make up a substance; changes in internal energy are of principal concern in thermodynamics
first law of thermodynamics
a restatement of the law of energy conservation, applied to systems in which energy is transferred by heat and/or work; the heat added to a system equals its increase in internal energy plus the external work it does on its environment
a process, often fast expansion or compression, in which no heat enters or leaves a system
a condition in which upward convection of air ceases, often because an upper region of the atmosphere is warmer than the region below it
second law of thermodynamics
thermal energy never spontaneously flows from a cold object to a hot object; also, no machine can be completely efficient in converting heat to work; some of the heat supplied to the machine at high temperature is dissipated as waste heat at lower temperature; and, finally, all systems tend to become more and more disordered as time goes by
a device that uses heat as input and provides work as output
a measure of the disorder of a system; whenever energy freely transforms from one form into another, the direction of transformation is toward a state of greater disorder and therefore toward one of greater entropy
ideal efficiency equation
ideal efficiency = (T hot - T cold)/T hot