Transcript Introduction to Modern Physics PHYX 2710

Physics of Technology
PHYS 1800
Lecture 22
Introduction
Section 0
Temperature
Lecture 1
Slide 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 1
PHYSICS OF TOF
ECHNOLOGY
- PHYS 1800
PHYSICS
TECHNOLOGY
ASSIGNMENT SHEET
Spring 2009Spring
Assignment
Sheet
2009
Date
Day
Lecture
Chapter
Feb 16
M
Presidents Day
17
Tu
Angular Momentum (Virtual Monday)
18
W
Review
19
H
Test 2
20
F*
Static Fluids, Pressure
Feb 23
M
Flotation
25
W
Fluids in Motion
27
F*
Temperature and Heat
Mar 2
M
First Law of Thermodynamics
4
W
Heat flow and Greenhouse Effect
6
F*
Climate Change
Mar 9-13
M-F
Spring Break
Mar 16
M
Heat Engines
18
W
Power and Refrigeration
20
F*
Electric Charge
Mar 23
M
Electric Fields and Electric Potential
25
W
Review
26
H
Test 3
27
F*
Electric Circuits
Mar 30
M
Magnetic Force Review
Apr 1
W
Electromagnets
3
F
Motors and Generators
Apr 6
M
Making Waves
8
W
Sound Waves
10
F*
E-M Waves, Light and Color
Apr 13
M
Mirrors and Reflections
Introduction
Section
0 Lecture 1 Slide 2
15
W
Refraction and Lenses
17
F*
Telescopes and Microscopes
Apr 20
M
Review
22
W
Seeing Atoms
24
F
The really BIG & the really small
INTRODUCTION TO Modern Physics PHYX 2710
May
1
F
Final Exam: 09:30-11:20am
No Class
8
5-8
5-8
9
9
9
10
10
10
No Classes
11
11
12
12
13
9-12
13
14
9-12
14
15
15
16
17
17
17
1-17
18 (not on test)
21 (not on test)
Homework Due
-
6
7
8
-
9
10
11
No test week
12
Fall 2004
* = Homework Handout
*Homework Handout
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 2
Physics of Technology
PHYS 1800
Lecture 19
Temperature
Section 0 Lecture 1 Slide 3
Temperature
on an Atomic Scale
Introduction
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 3
Describing Motion and Interactions
Position—where you are in space (L or meter)
Velocity—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast velocity is changing with time (LT-2 or m/s2)
Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N)
Inertia (mass)— a measure of the force needed to change the motion of a body (M)
Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 or N-m or J)
Work is equal to the force applied times the distance moved. W = F d
Kinetic Energy is the energy associated with an object’s motion. KE=½ mv2
Potential Energy is the energy associated with an objects position.
Gravitational potential energy PEgravity=mgh
Spring potential energy PEapring= -kx
Momentum— the potential of an object to induce motion in another object (MLT-1 or kg-m/s)
Introduction
Section 0
Lecture 1
Slide 4
Angular Momentum and Rotational Energy— the equivalent constants of motion for rotation (MT-1 or
kg/s) and (MLT-2 or kg m/s2 or N)
Modern Physics PHYX 2710
Pressure— forceINTRODUCTION
dividedTOby
the area over which the force is applied (ML-1T-1 or kg/m-s or N/m2 or Pa)
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 4
Dennison’s Laws Thermal Poker
(or How to Get a Hot Hand in Physics)
• 0th Law: Full House beats Two Pairs
• 1st Law: We’re playing the same game (but with a wild card)
• 2nd Law: You can’t win in Vegas.
• 3rd Law: In fact, you always loose.
• 0th Law: Defines Temperature
• 1st Law: Conservation of Energy (with heat)
•
2nd
Introduction
Section 0
Lecture 1
Slide 5
Law: You can’t recover all heat losses
(or defining entropy)
INTRODUCTION TO Modern Physics PHYX 2710
•
Fall 2004
3rd
Law: You can never get to absolute 0.
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 5
Heat
• What is heat?
• What is the relationship between quantity of heat
and temperature?
• What happens to a body (solid, liquid, gas) when
thermal energy is added or removed?
Thermal Energy
Solid: Atoms vibrating in all directions about their
fixed equilibrium (lattice) positions. Atoms
constantly colliding with each other.
Liquid: Atoms still oscillating and colliding with
each other but they are free to move so that the long
range order (shape) of body is lost.
Introduction Section 0 Lecture 1 Slide 6
Gas: No equilibrium position, no oscillations, atoms
are free and move in perpetual high-speed “zig-zag”
dance punctuated by collisions.
solid
liquid
INTRODUCTION TO Modern Physics PHYX 2710
gas
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 6
Heat
k BT  12 mv 2
kB is Boltzmann’s
constant
+
+
+
+
Lecture 1
+
+
Section 0
+
Introduction
+
+
=1.38 10-23 J/K
Slide 7
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 7
Physics of Technology
PHYS 1800
Lecture 19
Temperature
Introduction
Lecture 1 Slide 8
Measuring
Temperature
(0th Law of Thermodynamics)
Section 0
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 8
What is Temperature?
• If two objects are in contact with one another long
enough, the two objects have the same
temperature.
• This begins to define temperature, by defining
when two objects have the same temperature.
– When the physical properties are no longer changing,
the objects are said to be in thermal equilibrium.
– Two or more objects in thermal equilibrium have the
same temperature.
– This is the zeroth law of thermodynamics.
Introduction
Section 0
Lecture 1
Slide 9
– Corollary: Heat flows from hot to cold (DUH!!!)
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 9
Temperature and Heat
• When two objects at different temperatures are placed in
contact, heat will flow from the object with the higher
temperature to the object with the lower temperature.
• Heat added increases temperature, and heat removed
decreases temperature.
• Heat and temperature
are not the same.
• Temperature is a
quantity that tells us
which direction the
heat will flow.
Introduction
Section 0 Lecture
Heat is a form
of energy.
(Here comes
conservation of energy!!!)
1
Slide 10
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 10
• The first widely used temperature
scale was devised by Gabriel
Fahrenheit.
• Another widely used scale was
devised by Anders Celsius.
• The Celsius degree is larger than
the Fahrenheit degree: the ratio of
Fahrenheit degrees to Celsius
degrees is 180/100, or 9/5.
5
TC  TF  32 
9
9
TF  TC  32
5
• They are
both Section
equal
-40.
Introduction
0 at
Lecture
1
Slide 11
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 11
Temperature Ranges
0K
Absolute zero
-273.15 ºC
4.25
Liquid He boils
-268.9
20.4
Liquid H boils
-253
77
Liquid N2 boils
-196
90
Liquid O2 boils
-183
194
CO2 (dry ice) freezes
-79
273
Water freezes
0
310
Body temperature
~ 37
1336
Gold melts
1063
Carbon arc
5500
Sun’s photosphere
6000
Iron Welding arc
6020
5773
Introduction
Section 0
6273
6293
Lecture 1
Slide 12
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 12
Introduction
Section 0
Lecture 1
Slide 13
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 13
• The zero point on the
Fahrenheit scale was based on
the temperature of a mixture of
salt and ice in a saturated salt
solution.
• The zero point on the Celsius
scale is the freezing point of
water.
• Both scales go below zero.
• Is there such a thing as
absolute zero?
Introduction
Section 0
Lecture 1
Slide 14
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 14
What is absolute zero?
•
•
•
•
If the volume of a gas is
kept constant while the
temperature is increased,
the pressure will increase.
This can be used as a
means of measuring
temperature.
A constant-volume gas
thermometer allows the
pressure to change with
temperature while the
volume is held constant.
The difference in height of
the two mercury columns
is proportional to the
pressure.
Introduction Section 0 Lecture
1
Slide 15
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 15
Absolute zero
• We can then plot the pressure of a gas as a function of the
temperature.
• The curves for different gases or amounts are all straight lines.
• When these lines are extended backward to zero pressure, they
all intersect at the same temperature, -273.2C.
• Since negative pressure has no meaning, this suggests that the
temperature can never get lower than -273.2C, or 0 K (kelvin).
TK  TC  273.2

Introduction
Section 0
Lecture 1
Slide 16
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 16
Absolute zero and the 3rd Law of Thermodynamics
• Can anything ever get colder than 0 K?
• No.
• Can absolute zero ever be reached?
• No.
TK  TC  273.2

Introduction
Section 0
Lecture 1
Slide 17
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 17
Physics of Technology
Next Lab/Demo:
Fluid Dynamics
Temperature
Thursday 1:30-2:45
ESLC 46
Ch 9 and 10
Next Class:
Wednesday 10:30-11:20
BUS
Slide 18318 room
Review Ch 10
Introduction
Section 0
Lecture 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Temperature
Lecture 22 Slide 18