phy 113 a general physics i 9-9:50 am mwf olin 101 plan for lecture 30:
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PHY 113 A General Physics I 9-9:50 AM MWF Olin 101 Plan for Lecture 30: Chapter 20: First law of thermodynamics Concept of internal energy Examples of thermodynamic processes Note: We will not stress energy transfer processes in this class. iclicker question: - PowerPoint PPT PresentationTRANSCRIPT
PHY 113 A Fall 2012 -- Lecture 30 111/14/2012
PHY 113 A General Physics I9-9:50 AM MWF Olin 101
Plan for Lecture 30:
Chapter 20: First law of thermodynamics
1. Concept of internal energy
2. Examples of thermodynamic processes
3. Note: We will not stress energy transfer processes in this class
PHY 113 A Fall 2012 -- Lecture 30 211/14/2012
PHY 113 A Fall 2012 -- Lecture 30 311/14/2012
iclicker question:Concerning review session for Exam 3 ??
A. yesB. no
PHY 113 A Fall 2012 -- Lecture 30 411/14/2012
Thermodynamic processes: Q: heat added to system (Q>0 if TE>TS) W: work done on system (W>0 if
system expands
f
i
f
i
V
V
T
T
PdVW
dTTCQ )(
PHY 113 A Fall 2012 -- Lecture 30 511/14/2012
iclicker question:What happens to the “system” when Q and W are applied?
A. Its energy increasesB. Its energy decreaseC. Its energy remains the sameD. Insufficient information to answer question
PHY 113 A Fall 2012 -- Lecture 30 611/14/2012
Internal energy of a system
Eint(T,V,P….)
The internal energy is a “state” property of the system, depending on the instantaneous parameters (such as T, P, V, etc.). By contrast, Q and W describe path-dependent processes.
),,(),,( intintint iiifff PVTEPVTEE
PHY 113 A Fall 2012 -- Lecture 30 711/14/2012
First law of thermodynamics:
WQE int
Ei Ef
Q W
PHY 113 A Fall 2012 -- Lecture 30 811/14/2012
Applications of first law of thermodyamics
System ideal gas
nRTPV
pressure in Pascals
volume in m3 # of moles
temperature in K
8.314 J/(mol K)
PHY 113 A Fall 2012 -- Lecture 30 911/14/2012
Ideal gas -- continued
..............................
diatomicfor
monoatomicfor
gas ideal of on type dependingparameter
1
1
1
1 :energy Internal
:state ofEquation
57
35
int
PVnRTE
nRTPV
PHY 113 A Fall 2012 -- Lecture 30 1011/14/2012
iclicker question:We are about to see several P-V diagrams. Why is this helpful?
A. It will help us analyze the thermodynamic work
B. Physicists like nice graphsC. It is not actually helpful
PHY 113 A Fall 2012 -- Lecture 30 1111/14/2012
Constant volume process on an ideal gas
PVnRTE
nRTPV
1
1
1
1 :energy Internal
:state ofEquation
int
P
V
Pf Vf=Vi
Pi Vi
1
0
int
iif VPP
QE
W
PHY 113 A Fall 2012 -- Lecture 30 1211/14/2012
Constant pressure process on an ideal gas
PVnRTE
nRTPV
1
1
1
1 :energy Internal
:state ofEquation
int
P
V
Pf = Pi VfPi Vi
1
1int
ifi
ifi
ifi
VVPQ
VVPE
VVPW
PHY 113 A Fall 2012 -- Lecture 30 1311/14/2012
Constant temperature process on an ideal gas
PVnRTE
nRTPV
1
1
1
1 :energy Internal
:state ofEquation
int
f
iii
i
f
V
V
P
PVP
V
VnRT
PdVWQ
Ef
i
ln
ln
0int
PHY 113 A Fall 2012 -- Lecture 30 1411/14/2012
Consider the process described by ABCA
iclicker exercise:What is the net change in total energy?
A. 0B. 12000 JC. Who knows?
PHY 113 A Fall 2012 -- Lecture 30 1511/14/2012
Consider the process described by ABCA
iclicker exercise:What is the net heat added to the system?
A. 0B. 12000 JC. Who knows?
PHY 113 A Fall 2012 -- Lecture 30 1611/14/2012
Consider the process described by ABCA
iclicker exercise:What is the net work done on the system?
A. 0B. -12000 JC. Who knows?
PHY 113 A Fall 2012 -- Lecture 30 1711/14/2012
Webassign problem # 4: