Thermodynamics
Mark Lesmeister
Dawson High School
Physics
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Energy Transfer
• Energy can be transferred to (or from) a
system in various ways:
– Work can be done on (or by) the system.
– Heat can be transferred to (or from) the
system by
• Conduction.
• Convection.
• Radiation.
Mechanical Equivalent
of Heat
• Energy transferred to a system can become
potential energy, kinetic energy or internal energy.
From Harper's New Monthly Magazine, No. 231, August, 1869. Retrieved from Wikipedia
Commons, May 2013.
1st Law of
Thermodynamics
• The change in the energy of a system is
equal to the work done on the system
plus the heat and radiant energy
absorbed by the system.
• The total energy of an isolated system
does not change.
W  H  E
1st Law of
Thermodynamics
• A roller coaster illustrates the First Law.
Reversibility
• http://jersey.uoregon.edu/vlab/Thermodyn
amics/index.html
• 2 Guys, 500 Pillows
The Second Law of
Thermodynamics
• A system left to itself
tends to go to a state
with less order.
– Increasing disorder
decreases the energy
available to do work.
KE
PE
U
Entropy
• Entropy is a measure
of the “disorder” in a
system.
• According to the 2nd
Law of
Thermodynamics, the
entropy of the
universe increases.
• The entropy of a
closed system
increases unless
work is done.