University Physics Volume 2

# Key Terms

### Key Terms

Carnot cycle
cycle that consists of two isotherms at the temperatures of two reservoirs and two adiabatic processes connecting the isotherms
Carnot engine
Carnot heat engine, refrigerator, or heat pump that operates on a Carnot cycle
Carnot principle
principle governing the efficiency or performance of a heat device operating on a Carnot cycle: any reversible heat device working between two reservoirs must have the same efficiency or performance coefficient, greater than that of an irreversible heat device operating between the same two reservoirs
Clausius statement of the second law of thermodynamics
heat never flows spontaneously from a colder object to a hotter object
coefficient of performance
measure of effectiveness of a refrigerator or heat pump
cold reservoir
sink of heat used by a heat engine
disorder
measure of order in a system; the greater the disorder is, the higher the entropy
efficiency (e)
output work from the engine over the input heat to the engine from the hot reservoir
entropy
state function of the system that changes when heat is transferred between the system and the environment
entropy statement of the second law of thermodynamics
entropy of a closed system or the entire universe never decreases
heat engine
device that converts heat into work
heat pump
device that delivers heat to a hot reservoir
hot reservoir
source of heat used by a heat engine
irreversibility
phenomenon associated with a natural process
irreversible process
process in which neither the system nor its environment can be restored to their original states at the same time
isentropic
reversible adiabatic process where the process is frictionless and no heat is transferred
Kelvin statement of the second law of thermodynamics
it is impossible to convert the heat from a single source into work without any other effect
perfect engine
engine that can convert heat into work with $100%100%$ efficiency
perfect refrigerator (heat pump)
refrigerator (heat pump) that can remove (dump) heat without any input of work
refrigerator
device that removes heat from a cold reservoir
reversible process
process in which both the system and the external environment theoretically can be returned to their original states
third law of thermodynamics
absolute zero temperature cannot be reached through any finite number of cooling steps