Here are two examples of hydraulic devices and how they apply Pascal's principle: Brakes in cars - When the brake pedal is pressed, it pushes hydraulic fluid through the brake lines and into the brake calipers at each wheel. This increases the fluid pressure which is then used to push the brake pads against the rotor, creating friction to slow the wheel down. The pressure is multiplied through the hydraulic system, allowing a person to stop a multi-ton vehicle using only the force of one foot. Hydraulic lifts - Used to lift heavy equipment and machinery. When the lift arm is pressed down on, it decreases the volume in the hydraulic cylinder and increases the pressure. This high-pressure fluid is then sent to the

1. Module 3 Part 2
Temperature and Heat
Dr. Paul H. Comitz
pcomitz@live.com

2. Agenda
 Temperature and Heat Transfer
 Temperature
 Heat Transfer and Heat Flow
 Specific Heat
 Thermal Expansion
 Discussion:
 Pascal's Principle
 Lab : Temperature and Heat
 http://phet.colorado.edu/en/simulation/balloons-
and-buoyancy

3. Course Modules
# Module Weeks Reading Quiz
1 Newton's laws 1 Ch 4,5 *
2 Conservation of Energy and
Momentum
2,3 Ch 6,7,8 Quiz 1
3 Thermodynamics 4,5 Ch 12,13,14
4 Electromagnetism 6,7 Ch 17,18 Quiz 2
5 Waves, Sound, and Light 8,9 Ch 16, 20, 21 Quiz 3
6 Modern Physics 10 Ch 23 Final Exam
* it is strongly recommended you read chapters 0 - 3

4. Module 3
 Reading: Chapters 12,13,14
 Chapter 12 – Matter
 Chapter 13 - Fluids
 Chapter 14 – Temperature and Heat Transfer
 The Physics Classroom
 http://www.physicsclassroom.com/class/thermalP
 Exercise 3, due start of week 6 (4%)
 Discussion 2– due tonight (5%)
 Labs
 Gas Properties (3.75%)
 Temperature and Heat (3.75%)

5. Temperature
Temperature
 a number that corresponds to the warmth or
coldness of an object
 measured by a thermometer
 is a per-particle property
 no upper limit
 definite limit on lower end

6. Temperature
Temperature is proportional to the average kinetic
energy per particle in a substance.
• gas—how fast the gas particles are bouncing to
and fro
• liquid—how fast particles slide and jiggle past one
another
• solid—how fast particles move as they vibrate and
jiggle in place

7. Temperature
 Heat is a form of energy
 Heat flows from hot to cold
 Second law of Thermodynamics
 Heat flows from an area of higher
temperature to an area of lower
temperature
 There is no heat flow between areas of
equal temperature
 Temperature refers to an exchange of
energy

8. There is twice as much molecular kinetic energy in 2 liters
of boiling water as in 1 liter of boiling water. Which will
be the same for both?
A. temperature
B. thermal energy
C. both A and B
D. neither A nor B
Temperature
CHECK YOUR UNDERSTANDING

9. There is twice as much molecular kinetic energy in 2 liters
of boiling water as in 1 liter of boiling water. Which will
be the same for both?
A. temperature
B. thermal energy
C. both A and B
D. neither A nor B
Explanation:
Average kinetic energy of molecules is the same,
which means temperature is the same for both.
Temperature
CHECK YOUR ANSWER

10. To say that body A has a higher temperature than body B is to say
that body A has more
A. thermal energy.
B. mass.
C. kinetic energy per particle.
D. potential energy.
Temperature
CHECK YOUR UNDERSTANDING

11. To say that body A has a higher temperature than body B is to say
that body A has more
A. thermal energy.
B. mass.
C. kinetic energy per particle.
D. potential energy.
Temperature
CHECK YOUR ANSWER

12. Temperature Scales
 Celsius scale named after Anders Celsius (1701
–1744)
 zero C for freezing point of water to 100C for boiling
point of water
 Fahrenheit scale named after G. D. Fahrenheit
(1686–1736)
 32F for freezing point of water to 212F for boiling point
of water
 Kelvin scale named after Lord Kelvin (1824–1907)
0 K for freezing point of water to 373 K for boiling
point of water
 zero at absolute zero, same size degrees as Celsius scale
 Kelvins, rather than degrees are used

13. Temperature Conversions
Measuring with fixed reference points
 Celsius
 Fahrenheit
 Kelvin
 Rankine
 Conversions
 TK= TC+ 273
 TR = TF + 460
 TC = 5/9(TF - 32)
 TF = 9/5(TC) + 32

14. Heat
 A form of internal kinetic and potential energy
 Measured in
 joules
 1 joule = 1 kg m2/s2
 calorie
 1 calorie = 4.19J
 kilocalorie
 1 kilocalorie 4190 J
 BTU
 1 BTU = 1055 J

15. Heat
 1 kilocalorie is defined as the
amount of heat necessary to raise
1kg of water by 1 degree C
 1 BTU is the amount of heat
necessary to raise 1 lb. of water , 1
degree C
 1 calorie is the amount of heat
necessary to raise 1g of water by 1
degree C
 1 food calorie – 1 kilocalorie

16. Heat Transfer
 Second Law of Thermodynamics
 Heat flows from hot to cold
 Hot Cold
 Forms of heat transfers
 Conduction
 Convection
 Radiation

17. Heat Transfer by Conduction
 Heat transfer from warm to cold due to
molecular collisions
 Conductors
 Copper
 Aluminum
 Steel
 Insulators
 Glass
 Asbestos
 Wood
 Styrofoam

18. Heat Transfer by Convection
 Transfer of heat by the
movement of warm molecules
from one region of a gas or
liquid to another
 Convective Weather
 Sun heats earths surface
 Cooler air is warmed and rises
 Causes wind, clouds, rain

19. Heat Transfer by Radiation
 Heat transfer through energy
transmitted in the form of rays and
waves
 All life on earth depends on
transfer of energy from the sun
 Radiated heat is a form of an
electromagnetic wave

20. Heat Flow and Thermal Conductivity
 Similar to flow of electricity
 Formula
 Q = Kat(T2 – T1) /L
 Q = heat transferred in J or BTU
 K = thermal conductivity
 A = Area
 L = Thickness
 T2 = temperature of hot side
 T1 = temperature of cold side

21. Thermal Conductivity
Good
 Copper 380
 Aluminum 230
 Brass 120
 Steel 45
Poor
 Foam 0.035
 Air 0.025
 Water 0.56
 Glass 0.75

22. Specific Heat
 Measure of capacity to absorb
or give off heat
 Definition:
 the quantity of heat required
to change the temperature of
1 kg of a substance by 1
degree Celsius
 Thermal inertia—resistance
of a substance to a change
in temperature

23. Specific Heat Capacity
The high specific heat capacity of water
 has higher capacity for storing energy than almost any
other substance

24. Specific Heat Affects Climate
 Specific heat affects climate
 for Europeans, the Atlantic Ocean current carries
warm water northeast from the Caribbean regions and
retains much of its internal energy long enough to
reach the North Atlantic Ocean. Energy released is
carried by westerly winds over the European
continent.

25. Which has the higher specific heat capacity, water or land?
A. Water.
B. Land.
C. both of the above are the same
D. neither of the above
Specific Heat Capacity
CHECK YOUR UNDERSTANDING

26. Which has the higher specific heat capacity, water or land?
A. Water.
B. Land.
C. both of the above are the same
D. neither of the above
Explanation:
A substance with small temperature changes for large heat
changes has a high specific heat capacity. Water takes much
longer to heat up in the sunshine than does land. This difference
is a major influence on climate.
Specific Heat Capacity
CHECK YOUR ANSWER

27. Thermal Expansion
Thermal expansion
 due to rise in temperature of a substance, molecules
jiggle faster and move farther apart
 most substances expand when heated and contract
when cooled
 railroad tracks laid on winter days expand and buckle
in hot summer
 warming metal lids on glass jars under hot water
loosens the lid by more expansion of the lid than the
jar

28. Thermal Expansion
Thermal expansion (continued)
 plays a role in construction and devices
example:
• use of reinforcing steel with the same rate of
expansion as concrete—expansion joints on bridges
• gaps on concrete roadways and sidewalks allow for
concrete expansion in the summer and contraction in
the winter

29. When stringing telephone lines between poles in the summer, it is
advisable to allow the lines to
A. sag.
B. be taut.
C. be close to the ground.
D. allow ample space for birds.
Thermal Expansion
CHECK YOUR UNDERSTANDING

30. When stringing telephone lines between poles in the summer, it is
advisable to allow the lines to
A. sag.
B. be taut.
C. be close to the ground.
D. allow ample space for birds.
Explanation:
Telephone lines are longer in a warmer summer and shorter in a cold winter.
Hence, they sag more on hot summer days than in winter. If the lines are not
strung with enough sag in summer, they might contract too much and snap during
the winter—especially when carrying ice.
Thermal Expansion
CHECK YOUR ANSWER

31. Change of Phase
 Change in a substance from one form to
another
 Fusion - Solid to Liquid
 Freezing – Liquid to Solid
 Vaporization – liquid to gas
 Condensation – gas to liquid
 Triple Point – the temperature and pressure
at which the solid, liquid, and gas phases
exist simultaneously

32. In Class Discussion
Pascal’s Principle (text 13.2)
 Pascal’s principle states that a change in pressure in one part of a fluid is
transmitted to every other part; this is also the principle behind hydraulics.
Hydraulic devices can be used to multiply an applied force with the trade-off of
having to apply the force over a greater distance. Hydraulic devices are
commonly found in many areas of everyday life.
 In this discussion, you need to:
 Research and identify a device that uses hydraulics to operate. Use the ITT Tech
Virtual Library and other resources for your research.
 In your own words, describe the device and the method to apply Pascal’s principle to it.
Use two examples to illustrate your explanation.
 Include references to all sources you used in your research and posting.
 Requirements:
 Provide a complete, well-thought-out response.
 Approx. 1 page (200 to 250 words)
 Bring your completed work to next class
 Be prepared to briefly present your response to the class