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Unformatted text preview: PHYS 2101 Spring 2011 1. Thermodynamic Processes
A. Isobaric
B. Isochoric
C. Isothermal
D. Adiabatic
2. Ideal Gas Law PHYS 2101 EX1: Spring 2011 1.0kg of water at 100° C is converted to steam at 100° C
by boiling it at 1 atm. The volume of the water changes
from 1 x 103 m3 to 1.671 m3 as steam.
(a) Whatmuch work is is iagramthe system during this
d)
c)
b) How is the energy done by for this internal energy
does the PV d transferred as heat during the
change of the system’s process look
process? process?
like?
during the PHYS 2101 The graph below shows five isotherms (constant
temperature). Which isotherm is at the highest
temperature? P CT1: Spring 2011 V 1  Blue 2  Red 4  Purple 3  Green 5  Orange 6  All of them are at the same temperature PHYS 2101 For a gas initially in state 1, what happens to the
temperature of the gas if it undergoes an isobaric
expansion? P CT2: Spring 2011 1 V 1  The temperature will increase
2  The temperature will decrease
3  The temperature will stay the same PHYS 2101 In which of the following processes is the most work
done on the gas during a compression? P CT3: Spring 2011 V
I sot herm # 1 1  Isotherm #1 Adiabat # 1 I sot herm # 2 2  Isotherm #2 3  Adiabat #1 4  The work is the same for both isotherms.
5  The work is the same for all three processes. PHYS 2101 What happens to the temperature of the gas during an
adiabatic expansion? P CT4: Spring 2011 V
I sot herm # 1 Adiabat # 1 I sot herm # 2 1  The temperature increases.
2  The temperature decreases.
3  The temperature stays the same. PHYS 2101 What happens to the internal energy of the gas during
an adiabatic expansion? P CT5: Spring 2011 V
I sot herm # 1 Adiabat # 1 I sot herm # 2 1  The energy increases.
2  The energy decreases.
3  The energy stays the same. PHYS 2101 A particular cycle proceeds from A to B to C and back
particular
At the end of the cycle, what can be saida
to A. Along which step(s) of the cycle is there done by
work about
net energy transfer during
transferwork done by the gas?the cycle?
he gas?of energy?
A B P CT6: Spring 2011 C
V The B work is positive.
1  A to netgained during a complete cycle.
Heat is
The C work is negative.
2  B to netlost during a complete cycle.
Heat is
The A transfer of energy is zero.
3  C to net work is zero. PHYS 2101 Spring 2011 Thermodynamic Processes and the First Law
Process
Process Definition
Definition What It
What It
Means
Means 1st Law
1 Law Isochoric
Isochoric Constant
Constant
volume
volume Wby=0
W =0 ∆ Eint=Q
∆ E =Q Isothermal
Isothermal Constant
Constant
temperature
temperature ∆ Eint=0
∆ E =0 Q=Wby
Q=W Adiabatic
Adiabatic No heat in or
out Q=0 ∆ Eint=Wby Isobaric
Isobaric Constant
pressure Graphically
simple ∆ Eint=QWby PHYS 2101 CT7: Spring 2011 Answer with all correct answers: A
1 P 2
4
3 1  Isobaric
2  Isothermal
3  Adiabatic
4  Isochoric
5  None of them
6  All of them V Starting from State A, in which process(es) is the the
does
heat
most work donedecrease?gas?
gas end the
added toup gas? the increase?
i emperatureatdone by gas?
tnternal workofthe gasthe
positive energy thelowest temperature?
expand?
by PHYS 2101 One mole of ideal gas is initially in State A, where its
pressure and volume are (V0,P0). It expands from
State A to State B, where its pressure and volume are
(3V0,1/2P0). It is then compressed back to its original
volume, before being returned to its initial state.
A P EX1: Spring 2011 C B V PHYS 2101 EX1: Spring 2011 a) What is the temperature of the gas at State A if
P0 = 3 x 105 Pa and V0 = 0.02 m3?
b) What is ∆ Eint if the gas taken from State A to State
B if P0 = 3 x 105 Pa and V0 = 0.02 m3 and the gas is
monatomic? PHYS 2101 EX1: Spring 2011 c) How much heat is added to the gas during this
step?
d) How much heat is added to the gas during the
entire cycle ? PHYS 2101 The figure shows five paths that a monatomic ideal
gas could take from State A to another state in the
PV diagram. For which path is ∆ E the greatest? 1 4 2 P CT2: Spring 2011 5 A
3
V 6  ∆ E is the same along all five paths PHYS 2101 The figure shows five paths that a monatomic ideal
gas could take from State A to another state in the
PV diagram. For which path is ∆ E the least? 1 4 2 P CT2: Spring 2011 5 A
3
V 6  ∆ E is the same along all five paths PHYS 2101 The figure shows five paths that a monatomic ideal
gas could take from State A to another state in the
PV diagram. For which paths is ∆ E the same? 1 4 2 P CT2: Spring 2011 5 A
3
V 6  ∆ E is the same along all five paths PHYS 2101 The figure shows five paths that a monatomic ideal
gas could take from State A to another state in the
PV diagram. Is the amount of energy added to the
system as heat the same along paths 1 and 5? 1 4 2 P CT2: Spring 2011 5 A
3
V 1  Yes 2  No ...
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