Physics 25-26 2.0 Flashcards
Exchanges both matter and energy
Open System
Cannot exchange matter but can exchange energy
Closed System
Cannot exchange either matter or energy
Isolated System
Work involves the movement of
Matter from one location to another
Heat is a transfer of
thermal energy from one location to another
Heat added to a system
by its surroundings
Work can be done on a
system by its surroundings
Work done on the system by the surroundings is considered
positive work because the energy of the system increases
Heat can flow out of the
system to its surroundings
Work can be done by a
system on its surroundings
Work done by a system on its surroundings considered
negative work because the energy of the system will decrease
That the total energy, including heat in a system and its surroundings remains constant
First Law of Thermodynamics
supported by
Joules experiments
When heat is added to a system, some of the
energy goes into increasing the internal energy of the system
Heat added to the system =
Mechanical energy + heat
The amount of heat put into a system must equal the amount
of mechanical energy plus heat lost by the system
The direction of energy flow in natural processes
The Second Law of Thermodynamics
Heat always flows naturally from a
hot object to a cold object but never naturally from a cold to a hot object
Flows from a high temperature area to a low temperature
Heat engine
A heat engine is a device that
converts heat into mechanical energy
Only some of the input heat can
be converted to mechanical energy
The remaining heat is expelled
as exhaust heat
Devices that convert heat into mechanical energy
Heat Pump
A thermo – electric converter
Heat engines
Christian Huggens recognized that a successful reciprocating
needs a force to drive the piston forward and a force to pull back
Gases generated by an explosion inside
the engine drove the piston forward
Hazards of explosion and because there was no
Powerful internal mechanism to pull the piston back so the machine could operate continuously
Otto van Guerike demonstrated forces of
vacuums
