Lecture 3
Temperature, Thermal expansion, and
Heat
((NJIT Physics,
y
Chapter
p
10))
http://web.njit.edu/~sirenko/Phys-103-2005/Phys-103-2012.htm
Physics 103 Spring 2012
2012
Andrei Sirenko, NJIT
1
Last Lecture: Bernoulli's Equation
Water flows
W
fl
smoothly
hl through
h
h the
h pipe
i shown
h
in
i the
h figure,
fi
descending
d
di
in the process. Rank the four numbered sections of pipe according to (a)
the volume flow rate RV through
g them,, (b)
( ) the flow speed
p
v through
g
them, and (c) the water pressure p within them, greatest first.
a) all tie;
b) 1, then 2 and 3 tie, 4 (wider means slower);
c) (c) 4, 3, 2, 1 (wider and lower mean more pressure)
2012
Andrei Sirenko, NJIT
2
What is Temperature anyway ?
Temperature is one of the basic SI quantities.
Cannot be expressed through kg-m-s
kg m s
2012
Andrei Sirenko, NJIT
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Temperature in C and F
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Andrei Sirenko, NJIT
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T=0 what is that?
P
T 273 15 C
T=-273.15
T
T=0 K
2012
Andrei Sirenko, NJIT
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Zero’th law of Thermodynamics
If bodies A and B are each in
thermal equilibrium with a
third
hi d body
b d T, then
h they
h are in
i
thermal equilibrium with each
other
2012
Andrei Sirenko, NJIT
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Temperature difference determines
the Heat transfer process
What is the direction for the heat
transfer Between a,b,c,d?
2012
Andrei Sirenko, NJIT
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Temperature difference determines
the Heat transfer process
What is the direction for the heat
transfer Between a,b,c,d?
2012
Andrei Sirenko, NJIT
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Zero’th law of Thermodynamics
If bodies A and B are each in
thermal equilibrium with a
third
hi d body
b d T, then
h they
h are in
i
thermal equilibrium with each
other
2012
Andrei Sirenko, NJIT
9
Pressure, Temperature, and
Speed of molecules
vrms
3RT
=
M
mNA is the molar mass M
1 2
mvavg ∼ T
2
1 2
3
K avg = mvavg
= k BT
2
2
k B − Boltzman Constant
Root-mean-square speed
K avg =
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Andrei Sirenko, NJIT
10
The Distribution of Molecular Speeds
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Linear thermal expansion
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2D and 3D expansion
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Thermal expansion (continued)
Why days are longer
During the Summer time?
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Thermal expansion (atomic model)
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Thermal expansion
What is the ocean level increase due to +1 C◦ global warming ?
Water linear expansion coefficient is ~69e-6/C
69e 6/C◦ at 20 C◦.
Average ocean depth is 4 km
2012
Andrei Sirenko, NJIT
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Properties of Water (H2O)
negative thermal expansion of water
between 0 and 4 C
Freezes at 0 C,
C boils at 100 C
negative thermal expansion
i ZrW
in
Z W2O8
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Andrei Sirenko, NJIT
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The Triple Point of Water
A triple-point cell, in which
solid ice, liquid water, and
water
t vapor coexist
i t in
i thermal
th
l
equilibrium. By international
agreement, the temperature of
this mixture has been defined
to be 273.16 K. The bulb of a
constant-volume
constant
volume gas
thermometer is shown inserted
into the well of the cell.
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Andrei Sirenko, NJIT
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Thermal Expansion: QZ#2
When is the Empire State building taller?
A.
B.
C.
D.
E.
On Mondays
During rush hour
On a sunny Summer day
During Moon eclipse
Valentines Day
2012
Andrei Sirenko, NJIT
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500149_e_Prospekt Klima-_72