President University Thermal Physics Lecture by Dr. Erwin Sitompul
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Textbook:
“Fundamentals of Physics”, Halliday, Resnick, Walker, John Wiley &
Sons, 8
th
Extended, 2008.
Syllabus:
Chapter 18:
First Law of Thermodynamics
Chapter 19:
Kinetic Theory
Chapter 20:
Second Law of Thermodynamics
Textbook and Syllabus
Thermal Physics
Grade Policy
Thermal Physics
Final Grade =
5
%
Notes + 11%
Homework
& Validation Test
+
18
% Quizzes +
28
% Midterm Exam +
38
% Final Exam + Extra Points
You are expected to
write
a note along the lectures to record
your own conclusions or materials which are not covered by the
lecture slides.
Your handwritten note will be collected on Lecture 11 (after Quiz
3), and given back to you on Lecture 12.
Handwritten note contributes 5% of final grade.
Homeworks
and validation tests
will be given in fairly regular
basis. The average of homework grades contributes 1
1
% of final
grade.
Written homeworks are to be submitted on
A4 papers
, otherwise
they will not be graded.
Grade Policy
Homeworks must be submitted
on time
,
one day
before the next
lecture. Late submission will be penalized by point deduction of
–
10·
n
, where
n
is the total number of lateness made.
There will be 3 quizzes. Only the best 2 will be counted. The
average of quiz grades contributes
18
% of final grade.
●
Heading of Written Homework Papers (Required)
Thermal Physics
Homework 2
Emelie Raturandang
0029202400058
21 March 2027
No.1. Answer: . . . . . . . .
Thermal Physics
Grade Policy
Midterm
(28%)
and final exams
(38)
follow the schedule released
by AAB (Academic Administration Bureau).
Make up of quizzes must be requested within
one week
after the
schedule of the respective quiz.
Make up for mid exam and final exam must be requested directly
to AAB.
Extra points will be given if you solve a problem in front of the
class. You will earn 1 or 2.
Lecture slides can be copied during class session. It is also
available on internet. Please check the course homepage regularly.
http://zitompul.wordpress.com
Thermal Physics
Chapter 18
First Law of Thermodynamics
Thermal Physics
Thermodynamics and Engineering
Chapter 18
First Law of Thermodynamics
One of the principal branches of physics that is closely related to
Engineering is
thermodynamics
.
Thermodynamics is the study of thermal energy and its
applications. The main concern is
heat
and
temperature
, and their
relation to
energy
and
work
.
Some relations between thermodynamics and engineering are:
Automobile engineers are concerned with the heating of a car
engine and the effect of temperature to engine efficiency.
Building physics engineers are concerned with the temperature
control inside a building.
Process engineers are concerned with the cooling or heating of
the material in the production lines.
Medical engineers are concerned with how a patient’s
temperature might distinguish between a viral infection or a
cancerous growth.
Electrical engineers are concerned on how to design appliances
and electronic devices which can work without overheating
problems.
Electrical Engineering students are concerned on how to pass
the Thermal Physics class with good grade....
Temperature
Chapter 18
First Law of Thermodynamics
The starting point in discussion of
thermodynamics is the concept of
temperature
and how it is measured.
As one of the seven SI base quantities,
temperature is measured on the
Kelvin
scale.
The unit is called
kelvins
, with the notation K.
The temperature of a body has no upper limit,
but it does have a lower limit, the absolute zero
temperature, 0 kelvins or 0 K.
The Zeroth Law of Thermodynamics
The properties of many bodies change as we alter their
temperature.
For example, as their temperature increases, the
volume
of a
liquid increases, the
length
of a metal rod increases, the
electrical
resistance
of a wire increases, the
pressure
exerted by a confined
gas increases.
We can use any one of these properties as the basis of an
instrument that will help us pin down the concept of temperature.
Assume that we have a
thermoscope
, an instrument with digital
display that will display increasing number if it is heated or
decreasing number if it is cooled.
Chapter 18
First Law of Thermodynamics
The Zeroth Law of Thermodynamics
We now put the thermoscope (body
T
) into
intimate contact with another body (body
A
).
The entire system is confined within a thick-
walled insulating box.
We let body
T
and body
A
be in
thermal
equilibrium
, where the value indicated by the
thermoscope does not change anymore.
Next, we put body
T
into intimate contact
with another body
B
. We let the two bodies
come to
thermal equilibrium
at the same
reading of the thermoscope.
The question: If we put bodies
A
and
B
into
intimate contact, are they immediately in
thermal equilibrium with each other?
Zeroth Law of Thermodynamics
:
“If bodies
A
and
B
are each in themal
equilibrium with a third body
T
, then
A
and
B
are in thermal equilibrium with each other.”
Chapter 18
First Law of Thermodynamics
Measuring Temperature
Chapter 18
First Law of Thermodynamics
The Triple Point of Water
To set up a temperature scale, we pick some
reproducible thermal phenomenon as a standard
fixed point and assign a certain Kelvin
temperature to its environment.
For technical reasons, the triple point of water is
selected. At this condition,
liquid water
,
solid ice
,
and
water vapor
coexist, at a certain value of
pressure and temperature.
By international convention, the triple point of
water has been assigned a value of 273.16 K.
?
Isn’t it supposed to be 273.15 K?
Measuring Temperature
Chapter 18
First Law of Thermodynamics
The Constant-Volume Gas Thermometer
The standard thermometer is based on the
pressure of a gas in a fixed volume.
As shown on the next figure, the thermometer
consists of a gas-filled bulb connected by a
tube to a mercury manometer.
By raising and lowering reservoir
R
, the
mercury level in the left arm of the U-tube can
always be brought to the zero of the scale to
keep the gas volume constant.
The temperature of any body in thermal
contact with the bulb is then defined to be:
C
: a constant
p
: the pressure exerted by the gas
The pressure
p
is given by:
p
0
: the atmospheric pressure
ρ
: the density of mercury
h
:
the difference between the
mercury levels
Measuring Temperature
Chapter 18
First Law of Thermodynamics
If we now put the bulb in a liquid with triple-
point temperature, the temperature now being
measured is:
With this thermometer, different
gases in the bulb give slightly
different results.
However, as we use smaller and
smaller amounts of gas
(decreasing
p
3
), the reading
converge nicely to a single
temperature.
After eliminating
C
, the temperature can be
given as:
The Celsius and Fahrenheit Scales
Chapter 18
First Law of Thermodynamics
In the Celsius scale (formerly called the
centigrade scale), the temperatures are
measured in degrees, and the Celsius
degree has the same size as the kelvin.
The zero of the Celsius scale is shifted to
a more convenient value than absolute
zero.
The Fahrenheit scale employs a smaller
degree than the Celsius scale and a
different zero of temperature.
Checkpoint
Chapter 18
First Law of Thermodynamics
The figure here shows three linear temperature scales with the
freezing and boiling points of water indicated.
(a)
Rank the degrees on these scales by size, greatest first.
(b)
Rank the following temperatures, highest first: 50°X, 50°W, and
50°Y.
(a)
A
l
l
t
i
e
(b)
5
0
°
X
,
5
0
°
Y
,
5
0
°
W
Problem
Chapter 18
First Law of Thermodynamics
Suppose you come across old scientific notes that describe a
temperature scale called Z on which the boiling point of water is
65.0°Z and the freezing point is –14.0°Z. To what temperature on
the Fahrenheit scale would a temperature of
T
= –98.0°Z
correspond?
Thermal Expansion
Chapter 18
First Law of Thermodynamics
When the temperature of an object is raised, the body usually
exhibit
thermal expansion
.
With the added thermal energy, the atoms can move a bit farther
from one another than usual, against the spring-like interatomic
forces that hold every solid together.
Such thermal expansion is a property of material. Some of which
can be put to common use. Thermometers and thermostats may
be based on the differences in expansion between the components
of a bimetal strip (see below).
Familiar liquid-in glass thermometers are based on the fact that
liquids such as mercury and alcohol expands to a different
(greater) extend than their glass containers.
Thermal Expansion
Chapter 18
First Law of Thermodynamics
Linear Expansion
In the temperature of a metal rod of length
L
is raised by an
amount
Δ
T
, its length is found to increase by an amount:
α
: coefficient of linear expansion
[/°C
or /K]
The coefficient of linear expansion
α
depends on the material. It also
varies with temperature. But, for
most practical purposes it can be
taken as constant for a certain
material.
Thermal Expansion
Chapter 18
First Law of Thermodynamics
Volume Expansion
If all dimensions of a solid expand with temperature, the volume of
that solid must also expand.
If the temperature of a solid or liquid whose volume is
V
is
increased by an amount
Δ
T
, the increase in volume is found to be:
β
: coefficient of volume expansion
[/°C
or /K]
?
Can you find the exact relation?
●
The same steel ruler at
two different temperature
Checkpoint
Chapter 18
First Law of Thermodynamics
The figure here shows four rectangular metal plates, with sides of
L
,
2
L
, or 3
L
. They are all made of the same material, and their
temperature is to be increased by the same amount.
Rank the plates according to the expected increase in
(a)
their vertical heights and
(b)
their areas,
greatest first.
(a)
2
a
n
d
3
t
i
e
,
t
h
e
n
1
,
t
h
e
n
4
(b)
3
,
t
h
e
n
2
,
t
h
e
n
1
a
n
d
4
t
i
e
Problem
Chapter 18
First Law of Thermodynamics
On a hot day in Las Vegas, an oil trucker loaded 37
000
l
of diesel
fuel. It encountered cold weather on the way to Utah, where the
temperature was 23.0 K lower than in Las Vegas, and where it
delivered its entire load.
How many liters did it deliver? The coefficient of volume expansion
for diesel fuel is 9.50×10
–4
/°C, and the coefficient of linear
expansion for its steel truck tank is 11×10
–6
/°C.
?
Who paid for the “missing” diesel fuel?
!
Although looked much, the missing fuel is
only 2.2 % of the original load.
Temperature and Heat
Chapter 18
First Law of Thermodynamics
The temperature of a cup of hot coffee, left sitting
on a table, will fall –rapidly at first but then more
slowly– until it reaches room temperature
The
room and the coffee are then in thermal
equilibrium.
Generalizing the situation, we describe the coffee
as a system (with temperature
T
S
) and the room
environment as another system (with
temperature
T
E
) .
Our observation is that if
T
S
≠
T
E
, then
T
S
will
change (
T
E
can also change some) until the two
temperatures are equal and thus thermal
equilibrium is reached.
Such a change in temperature is because of a
transfer of energy between the system and the
system’s environment. The transferred energy is
called
heat
and is symbolized with
Q
.
Heat is
positive
when energy is
absorbed
by the system.
Heat is
negative
when energy is
released
or lost by the system.
Temperature and Heat
Chapter 18
First Law of Thermodynamics
Heat is the energy transferred between a system and its
environment because of a temperature difference that exists
between them.
Besides, energy can also be transferred between a system and its
environment as work
W
via a force acting on a system.
By old definition, heat was measured in terms of its ability to raise
the temperature of water.
In SI system, the
calorie
(cal) was defined as the amount of heat
that would raise the temperature of 1 g of water from 14.5°C to
15.5°C.
In the British system, the
British thermal unit
(Btu) was defined
as the amount of heat that would raise the temperature of 1 lb of
water from 63°F to 64°F.
●
1 cal = 4.1868 Joule
Class Group Assignments
Chapter 18
First Law of Thermodynamics
1.
Unsatisfied with the Celsius and Fahrenheit temperature scales,
you decide to create your own. On your temperature scale, the ice
point is 77
M and the steam point is at 437
M, where “M” stands
for “my scale.” What temperature on your scale corresponds to
68
F?
(a) 154 °M
(d) 168 °M
(b) 140 °M
(e) 136 °M
(c) 149 °M
2.
A constant-volume gas thermometer is used to measure the
temperature of an object. When the thermometer is in contact with
water at its triple point (273.16 K), the pressure in the
thermometer is 8.950×10
4
Pa. When it is in contact with the
object, the pressure is 7.650×10
4
Pa. The temperature of the
object is:
(a) 23 K
(b) 233 K
(c) 310 K
(d) 314 K
(e) 2636 K
Class Group Assignments
Chapter 18
First Law of Thermodynamics
3.
A glass tube with the volume 200 cm
3
is completely filled with
mercury at 20°C. If the temperature of the system is increased to
100°C, determine the amount of mercury that overflows. The
coefficient of linear expansion of glass is 0.34×10
–5
K
–1
while
coefficient of volume expansion of mercury is 1.82×10
–4
K
–1
.
(a) 1.43 cm
3
(d) 2.72 cm
3
(b) 2.75 cm
3
(e) 3.57 cm
3
(c) 4.81 cm
3
4.
A brass cube, 10 cm on a side, is raised in temperature by 200°C.
The coefficient of volume expansion of brass is 57 × 10
–6
/°C. By
what percentage is any one of the 10-cm edges increased in
length?
(a) 4%
(d) 1.14%
(b) 0.38%
(e) 0.29%
(c) 0.17%
Class Group Assignments
Chapter 18
First Law of Thermodynamics
5.
A gram of distilled water at 4°C:
(a)
will increase slightly in weight when heated to 6°C.
(b)
will decrease slightly in weight when heated to 6°C.
(c)
will increase slightly in volume when heated to 6°C.
(d)
will decrease slightly in volume when heated to 6°C
.
(e)
will not change in either volume or weight.
Homework 1
1.
(18-7) Suppose that on a linear temperature scale X, water boils
at –53.5°X and freezes at –170°X. What is a temperature of 340 K
on the X scale? (Approximate water’s boiling point as 373 K.)
2.
(18-17) A steel rod is 3.000 cm in diameter at 25.00°C. A brass
ring has an interior diameter of 2.992 cm at 25.00°C. At what
common temperature will the ring just slide onto the rod? (
Hint
:
For coefficients, use only the value given by the textbook.)
Chapter 18
First Law of Thermodynamics
●
Be sure to understand the homework problems.
●
Validation tests will be conducted occasionally.
Deadline:
7
April 201
5
.
President University offers a Thermal Physics course with lectures delivered by Dr. Erwin Sitompul. The course covers topics like the First Law of Thermodynamics, Kinetic Theory, and the Second Law of Thermodynamics. Students are required to maintain handwritten notes, submit homework on time, and undergo regular assessments contributing to their final grade. The grading policy includes essays, quizzes, midterm, and final exams, with provisions for make-up requests and extra points for problem-solving. Additional details on the syllabus, submission guidelines, and exam schedules are provided in the course outline.
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Thermal Physics Lecture 1 Dr.-Ing. Erwin Sitompul President University http://zitompul.wordpress.com 2 0 1 6 President University Erwin Sitompul Thermal Physics 1/1
Thermal Physics Textbook and Syllabus Textbook: Fundamentals of Physics , Halliday, Resnick, Walker, John Wiley & Sons, 8th Extended, 2008. Syllabus: Chapter 18: First Law of Thermodynamics Chapter 19: Kinetic Theory Chapter 20: Second Law of Thermodynamics President University Erwin Sitompul Thermal Physics 1/2
Thermal Physics Grade Policy Final Grade = 5% Notes + 11% Homework & Validation Test + 18% Quizzes + 28% Midterm Exam + 38% Final Exam + Extra Points You are expected to write a note along the lectures to record your own conclusions or materials which are not covered by the lecture slides. Your handwritten note will be collected on Lecture 11 (after Quiz 3), and given back to you on Lecture 12. Handwritten note contributes 5% of final grade. Homeworks and validation tests will be given in fairly regular basis. The average of homework grades contributes 11% of final grade. Written homeworks are to be submitted on A4 papers, otherwise they will not be graded. President University Erwin Sitompul Thermal Physics 1/3
Thermal Physics Grade Policy Homeworks must be submitted on time, one day before the next lecture. Late submission will be penalized by point deduction of 10 n, where n is the total number of lateness made. There will be 3 quizzes. Only the best 2 will be counted. The average of quiz grades contributes 18% of final grade. Thermal Physics Homework 2 Emelie Raturandang 0029202400058 21 March 2027 No.1. Answer: . . . . . . . . Heading of Written Homework Papers (Required) President University Erwin Sitompul Thermal Physics 1/4
Thermal Physics Grade Policy Midterm (28%) and final exams (38) follow the schedule released by AAB (Academic Administration Bureau). Make up of quizzes must be requested within one week after the schedule of the respective quiz. Make up for mid exam and final exam must be requested directly to AAB. Extra points will be given if you solve a problem in front of the class. You will earn 1 or 2. Lecture slides can be copied during class session. It is also available on internet. Please check the course homepage regularly. http://zitompul.wordpress.com President University Erwin Sitompul Thermal Physics 1/5
Thermal Physics Chapter 18 First Law of Thermodynamics President University Erwin Sitompul Thermal Physics 1/6
Chapter 18 First Law of Thermodynamics Thermodynamics and Engineering One of the principal branches of physics that is closely related to Engineering is thermodynamics. Thermodynamics is the study of thermal energy and its applications. The main concern is heat and temperature, and their relation to energy and work. Some relations between thermodynamics and engineering are: Automobile engineers are concerned with the heating of a car engine and the effect of temperature to engine efficiency. Building physics engineers are concerned with the temperature control inside a building. Process engineers are concerned with the cooling or heating of the material in the production lines. Medical engineers are concerned with how a patient s temperature might distinguish between a viral infection or a cancerous growth. Electrical engineers are concerned on how to design appliances and electronic devices which can work without overheating problems. Electrical Engineering students are concerned on how to pass the Thermal Physics class with good grade.... President University Erwin Sitompul Thermal Physics 1/7
Chapter 18 First Law of Thermodynamics Temperature The starting point in discussion of thermodynamics is the concept of temperature and how it is measured. As one of the seven SI base quantities, temperature is measured on the Kelvin scale. The unit is called kelvins, with the notation K. The temperature of a body has no upper limit, but it does have a lower limit, the absolute zero temperature, 0 kelvins or 0 K. President University Erwin Sitompul Thermal Physics 1/8
Chapter 18 First Law of Thermodynamics The Zeroth Law of Thermodynamics The properties of many bodies change as we alter their temperature. For example, as their temperature increases, the volume of a liquid increases, the length of a metal rod increases, the electrical resistance of a wire increases, the pressure exerted by a confined gas increases. We can use any one of these properties as the basis of an instrument that will help us pin down the concept of temperature. Assume that we have a thermoscope, an instrument with digital display that will display increasing number if it is heated or decreasing number if it is cooled. President University Erwin Sitompul Thermal Physics 1/9
Chapter 18 First Law of Thermodynamics The Zeroth Law of Thermodynamics We now put the thermoscope (body T) into intimate contact with another body (body A). The entire system is confined within a thick- walled insulating box. We let body T and body A be in thermal equilibrium, where the value indicated by the thermoscope does not change anymore. Next, we put body T into intimate contact with another body B. We let the two bodies come to thermal equilibrium at the same reading of the thermoscope. The question: If we put bodies A and B into intimate contact, are they immediately in thermal equilibrium with each other? Zeroth Law of Thermodynamics: If bodies A and B are each in themal equilibrium with a third body T, then A and B are in thermal equilibrium with each other. President University Erwin Sitompul Thermal Physics 1/10
Chapter 18 First Law of Thermodynamics Measuring Temperature The Triple Point of Water To set up a temperature scale, we pick some reproducible thermal phenomenon as a standard fixed point and assign a certain Kelvin temperature to its environment. For technical reasons, the triple point of water is selected. At this condition, liquid water, solid ice, and water vapor coexist, at a certain value of pressure and temperature. By international convention, the triple point of water has been assigned a value of 273.16 K. 273.16 K T = ?Isn t it supposed to be 273.15 K? 3 President University Erwin Sitompul Thermal Physics 1/11
Chapter 18 First Law of Thermodynamics Measuring Temperature The Constant-Volume Gas Thermometer The standard thermometer is based on the pressure of a gas in a fixed volume. As shown on the next figure, the thermometer consists of a gas-filled bulb connected by a tube to a mercury manometer. By raising and lowering reservoir R, the mercury level in the left arm of the U-tube can always be brought to the zero of the scale to keep the gas volume constant. The temperature of any body in thermal contact with the bulb is then defined to be: T Cp = C p : a constant : the pressure exerted by the gas The pressure p is given by: p p = gh p0 h : the atmospheric pressure : the density of mercury : the difference between the mercury levels 0 President University Erwin Sitompul Thermal Physics 1/12
Chapter 18 First Law of Thermodynamics Measuring Temperature If we now put the bulb in a liquid with triple- point temperature, the temperature now being measured is: T Cp = 3 3 After eliminating C, the temperature can be given as: = p p p p = (273.16) T T 3 3 3 With this thermometer, different gases in the bulb give slightly different results. However, as we use smaller and smaller amounts of gas (decreasing p3), the reading converge nicely to a single temperature. President University Erwin Sitompul Thermal Physics 1/13
Chapter 18 First Law of Thermodynamics The Celsius and Fahrenheit Scales In the Celsius scale (formerly called the centigrade scale), the temperatures are measured in degrees, and the Celsius degree has the same size as the kelvin. The zero of the Celsius scale is shifted to a more convenient value than absolute zero. 273.15 T T = C The Fahrenheit scale employs a smaller degree than the Celsius scale and a different zero of temperature. 9 32 5 = + T T F C President University Erwin Sitompul Thermal Physics 1/14
Chapter 18 First Law of Thermodynamics Checkpoint The figure here shows three linear temperature scales with the freezing and boiling points of water indicated. (a) Rank the degrees on these scales by size, greatest first. (b) Rank the following temperatures, highest first: 50 X, 50 W, and 50 Y. (a) All tie (b) 50 X, 50 Y, 50 W President University Erwin Sitompul Thermal Physics 1/15
Chapter 18 First Law of Thermodynamics Problem Suppose you come across old scientific notes that describe a temperature scale called Z on which the boiling point of water is 65.0 Z and the freezing point is 14.0 Z. To what temperature on the Fahrenheit scale would a temperature of T = 98.0 Z correspond? 180 79.0 98.0 Z = 32 (84.0) F = 159.4 F President University Erwin Sitompul Thermal Physics 1/16
Chapter 18 First Law of Thermodynamics Thermal Expansion When the temperature of an object is raised, the body usually exhibit thermal expansion. With the added thermal energy, the atoms can move a bit farther from one another than usual, against the spring-like interatomic forces that hold every solid together. Such thermal expansion is a property of material. Some of which can be put to common use. Thermometers and thermostats may be based on the differences in expansion between the components of a bimetal strip (see below). Familiar liquid-in glass thermometers are based on the fact that liquids such as mercury and alcohol expands to a different (greater) extend than their glass containers. President University Erwin Sitompul Thermal Physics 1/17
Chapter 18 First Law of Thermodynamics Thermal Expansion Linear Expansion In the temperature of a metal rod of length L is raised by an amount T, its length is found to increase by an amount: = L L T : coefficient of linear expansion [/ Cor /K] The coefficient of linear expansion depends on the material. It also varies with temperature. But, for most practical purposes it can be taken as constant for a certain material. President University Erwin Sitompul Thermal Physics 1/18
Chapter 18 First Law of Thermodynamics Thermal Expansion Volume Expansion If all dimensions of a solid expand with temperature, the volume of that solid must also expand. If the temperature of a solid or liquid whose volume is V is increased by an amount T, the increase in volume is found to be: = V V 3 T : coefficient of volume expansion [/ Cor /K] = ?Can you find the exact relation? The same steel ruler at two different temperature President University Erwin Sitompul Thermal Physics 1/19
Chapter 18 First Law of Thermodynamics Checkpoint The figure here shows four rectangular metal plates, with sides of L, 2L, or 3L. They are all made of the same material, and their temperature is to be increased by the same amount. Rank the plates according to the expected increase in (a) their vertical heights and (b) their areas, greatest first. (a) 2 and 3 tie, then 1, then 4 (b) 3, then 2, then 1 and 4 tie President University Erwin Sitompul Thermal Physics 1/20
Chapter 18 First Law of Thermodynamics Problem On a hot day in Las Vegas, an oil trucker loaded 37000 l of diesel fuel. It encountered cold weather on the way to Utah, where the temperature was 23.0 K lower than in Las Vegas, and where it delivered its entire load. How many liters did it deliver? The coefficient of volume expansion for diesel fuel is 9.50 10 4/ C, and the coefficient of linear expansion for its steel truck tank is 11 10 6/ C. = V V (37000)(9.50 10 )( 23.0) 808.45l = T = 4 = = = delivered V V 37000 808.45 36191.55l V ?Who paid for the missing diesel fuel? ! Although looked much, the missing fuel is only 2.2 % of the original load. President University Erwin Sitompul Thermal Physics 1/21
Chapter 18 First Law of Thermodynamics Temperature and Heat The temperature of a cup of hot coffee, left sitting on a table, will fall rapidly at first but then more slowly until it reaches room temperature The room and the coffee are then in thermal equilibrium. Generalizing the situation, we describe the coffee as a system (with temperature TS) and the room environment as another system (with temperature TE) . Our observation is that if TS TE, then TS will change (TE can also change some) until the two temperatures are equal and thus thermal equilibrium is reached. Such a change in temperature is because of a transfer of energy between the system and the system s environment. The transferred energy is called heat and is symbolized with Q. Heat is positive when energy is absorbed by the system. Heat is negative when energy is released or lost by the system. President University Erwin Sitompul Thermal Physics 1/22
Chapter 18 First Law of Thermodynamics Temperature and Heat Heat is the energy transferred between a system and its environment because of a temperature difference that exists between them. Besides, energy can also be transferred between a system and its environment as work W via a force acting on a system. By old definition, heat was measured in terms of its ability to raise the temperature of water. In SI system, the calorie (cal) was defined as the amount of heat that would raise the temperature of 1 g of water from 14.5 C to 15.5 C. In the British system, the British thermal unit (Btu) was defined as the amount of heat that would raise the temperature of 1 lb of water from 63 F to 64 F. 1 cal = 4.1868 Joule President University Erwin Sitompul Thermal Physics 1/23
Chapter 18 First Law of Thermodynamics Class Group Assignments 1.Unsatisfied with the Celsius and Fahrenheit temperature scales, you decide to create your own. On your temperature scale, the ice point is 77 M and the steam point is at 437 M, where M stands for my scale. What temperature on your scale corresponds to 68 F? (a) 154 M (d) 168 M (b) 140 M (e) 136 M (c) 149 M 2.A constant-volume gas thermometer is used to measure the temperature of an object. When the thermometer is in contact with water at its triple point (273.16 K), the pressure in the thermometer is 8.950 104 Pa. When it is in contact with the object, the pressure is 7.650 104 Pa. The temperature of the object is: (a) 23 K (b) 233 K (c) 310 K (d) 314 K (e) 2636 K President University Erwin Sitompul Thermal Physics 1/24
Chapter 18 First Law of Thermodynamics Class Group Assignments 3.A glass tube with the volume 200 cm3 is completely filled with mercury at 20 C. If the temperature of the system is increased to 100 C, determine the amount of mercury that overflows. The coefficient of linear expansion of glass is 0.34 10 5 K 1 while coefficient of volume expansion of mercury is 1.82 10 4 K 1. (a) 1.43 cm3 (d) 2.72 cm3 (b) 2.75 cm3 (e) 3.57 cm3 (c) 4.81 cm3 4.A brass cube, 10 cm on a side, is raised in temperature by 200 C. The coefficient of volume expansion of brass is 57 10 6/ C. By what percentage is any one of the 10-cm edges increased in length? (a) 4% (d) 1.14% (b) 0.38% (e) 0.29% (c) 0.17% President University Erwin Sitompul Thermal Physics 1/25
Chapter 18 First Law of Thermodynamics Class Group Assignments 5.A gram of distilled water at 4 C: (a) will increase slightly in weight when heated to 6 C. (b) will decrease slightly in weight when heated to 6 C. (c) will increase slightly in volume when heated to 6 C. (d) will decrease slightly in volume when heated to 6 C. (e) will not change in either volume or weight. President University Erwin Sitompul Thermal Physics 1/26
Chapter 18 First Law of Thermodynamics Homework 1 1.(18-7) Suppose that on a linear temperature scale X, water boils at 53.5 X and freezes at 170 X. What is a temperature of 340 K on the X scale? (Approximate water s boiling point as 373 K.) 2.(18-17) A steel rod is 3.000 cm in diameter at 25.00 C. A brass ring has an interior diameter of 2.992 cm at 25.00 C. At what common temperature will the ring just slide onto the rod? (Hint: For coefficients, use only the value given by the textbook.) Deadline: 7 April 2015. Be sure to understand the homework problems. Validation tests will be conducted occasionally. President University Erwin Sitompul Thermal Physics 1/27
