# Shared Flashcard Set

## Details

Ch15
entropy , laws of thermodynamics, carnot engine and fridge
26
Physics
01/24/2013

Term
 The First Law of Thermodynamics is 1.name
Definition
 1.the law of conservation of energy
Term
 the law of conservation of energy def   ΔU=
Definition
 (ΔU)change in internal energy of a closed system will be equal to: the energy added to the system    (Q)                   -             the work done by                                                          the system on its                                                               surroundings.
Term
 If heat is added to a system ([image]) and no change in internal energy of the system occurs ([image]), then the system must do __________ work on the outside world.
Definition
 positive
Term
 An isothermal process def
Definition
 temperature does not change.
Term
 In order for an isothermal process to take place, we assume the system is in contact with a _______
Definition
 heat reservoir
Term
Definition
 there is no heat flow: IN or OUT of the system.
Term
 An isobaric process def
Definition
 occurs at constant pressure
Term
 isovolumetric process def
Definition
 constant volume
Term
 second law of thermodynamics def
Definition
 Heat CAN flow spontaneously from a hot object to a cold object; it will not flow spontaneously from a cold object to a hot object.
Term
 heat engine; mechanical energy can be obtained from thermal energy only when heat can flow from
Definition
 higher→lower temperature.
Term
 Heat Engines engines that run in a repeating cycle have a change in internal energy of _____ in a cycle , as the system returns to its initial state.
Definition
 zero
Term
 Carnot engine was created  in order to
Definition
 examine the efficiency of a heat engine.
Term
 Carnot engine ideal (2)
Definition
 1.has no friction 2.Each leg of its cycle is reversible
Term
 The Carnot cycle consists of
Definition
 • Isothermal expansion • Adiabatic expansion • Isothermal compression • Adiabatic compression
Term
 from the formula of the ideal reversible engine efficiency, why can we say that 100% efficiency is impossible?
Definition
 the cold reservoir(Tc ) has to be at absolute zero
Term
 why do Real engines only achieve 60-80% of the Carnot value of efficiency?
Definition
 loose heat due other things like friction
Term
 Refrigerators, Air Conditioners, and Heat Pumps how do these work? (think about the engine works)
Definition
 as heat engines in reverse: By doing work, heat is extracted from the cold reservoir (makes the fridge cold) and exhausted to the hot reservoir.
Term
 Another statement of the second law of thermodynamics( in reference to Entropy):   The total entropy of an isolated system never (increase /decrease.)
Definition
 The total entropy of an isolated system never decreases
Term
 Entropy def
Definition
 is a measure of the disorder of a system.   Natural processes tend to move toward a state of greater disorder.
Term
 Thermal equilibrium def
Definition
 the uniform final state has more disorder than the separate temperatures in the initial state.  ex:If you put milk and sugar in your coffee and stir it, you wind up with coffee that is uniformly milky and sweet. No amount of stirring will get the milk and sugar to come back out of solution. = only energy can seperate these components
Term
 the heat death of the universe def
Definition
 In any natural process, some energy becomes unavailable to do useful work.
Term
 Efficiency is always less
Definition
 than 1.
Term
 Entropy increases when heat is ______ , and decreases when heat is ________   (added or removed)
Definition