1

UNIVERSITY OF GUYANAFACULTY OF NATURAL SCIENCESDEPART. OF MATH, PHYS & STATS

PHY 110 – PHYSICS FOR ENGINEERSLECTURE 2

(FRIDAY, SEPT. 2, 2011)

2

1.1 Intro. & Concept of Temperature

Introduction:Temperature is a word that will be familiar to all readers, but it is also a word that poses scientific difficulty… We know what it feels like to touch a cold or hot object. Temperature is directly associated with the physiological sense of hotness. But one cannot measure temperature using a physiological effect because people are differently sensitive to hotness. Hot and cold are therefore imprecise terms on which it is difficult to base a scientific definition.

(Physics by Robert Hutchings 2nd Ed., pg 416)

3

1.1 Intro. & Concept of Temp. Cont’d

Left to Right: Outdoor thermometer; Galileo Galilei and Isaac Newton were early inventors of Thermometers. (Taken from Microsoft Student with Encarta Premium 2007)

4

1.1 Intro. & Concept of Temp. Cont’d

Heat:It is the transfer of energy solely on the

account of a temperature difference.Temperature:

It is measure of how hot or cold a body is.Thermal Energy:

This is the vibratory energy of molecules that constitute a body. Thus temperature is an indication of this energy.

5

1.1 Intro. & Concept of Temp. Cont’d

Temperature:It is a measure of the average kinetic energy of

the molecules that constitute a body.Macroscopic quantity – large scale and it is

measureable. (Base quantity)Our sense of perception is well acquainted with

it (we feel hotness and coldness)Thermodynamic quantity that indicates thermal

equilibrium (heat balance). Study of heat in motion. (Thermo = heat; dynamics = motion)

(Physics for the IB Diploma by Tim Kirk, pg 24.)

6

1.1 Intro. & Concept of Temp. Cont’d

Zeroth (0th)Law of Thermodynamics:It states that if two bodies A and B are in thermal

equilibrium with a third body C, then A and B are in thermal equilibrium with each other.

7

1.1 Intro. & Concept of Temp. Cont’d

Historical PerspectiveOne of the earliest temperature scales was

that devised by the German physicist Gabriel Daniel Fahrenheit. According to this scale, at standard atmospheric pressure, the freezing point (and melting point of ice) is 32° F, and the boiling point is 212° F. The centigrade, or Celsius scale, invented by the Swedish astronomer Anders Celsius, and used throughout most of the world, assigns a value of 0° C to the freezing point and 100° C to the boiling point.

8

1.1 Intro. & Concept of Temp. Cont’d

Historical Perspective Cont’dIn scientific work, the absolute or Kelvin

scale, invented by the British mathematician and physicist William Thomson, 1st Baron Kelvin, is most widely used. In this scale, absolute zero is at -273.15°C, which is zero K, and the degree intervals are identical to those measured on the Celsius scale .

9

1.1 Intro. & Concept of Temp. Cont’d

Temperature Scales:This is a standard used in the determination

of temperature.Construction of Temperature Scale:

1. Identify a thermometric substance i.e. one that has a physical property that is temperature dependent.

2. Identify the thermometric property i.e. Heat measuring property.

3. Identify two (2) fixed points – lower & upper by which the thermometer operates. Points used depends temperature scale.

10

1.1 Intro. & Concept of Temp. Cont’d

Types of Temperature Scales:Celsius/Centigrade: Assumes that equal changes in the thermometric property are produced by equal changes in temperature.

Fixed pts: ice pt and steam point of H2O Ice pt: Temperature where pure water in

solid & liquid phases co-exists at Standard Atmospheric Pressure (S.A.P – 1.01 × 105 Pa)

Steam pt: Temperature where pure water in liquid & vapour phases co-exists at S.A.P.

X

11

1.1 Intro. & Concept of Temp. Cont’d

Celsius Temperature:

Physics for the IB Diploma by Tim Kirk, pg 24.

CXXXX 0

0100

0 100

Value of Thermometric property at ice pt, steam pt and unknown Celsius temperature.

XXX ,, 1000

12

UNIVERSITY OF GUYANAFACULTY OF NATURAL SCIENCESDEPART. OF MATH, PHYS & STATS

PHY 110 – PHYSICS FOR ENGINEERSLECTURE 2

(THURSDAY, SEPT. 8, 2011)

13

Assessments:

Assignments – 10%:1. Individual: Two (2) Oral Quizz - 5%a) Heat – 2.5 %b) Properties of Matter – 2.5%2. Group: Power-Point Presentation - 5%c) Written Report – 2.5 %d) Oral Presentation (15 min.) – 2.5 %e) Topics based on the course outline.f) Each Tutorial group conducts two (2)

presentations.

14

Assessments Cont’d:

Group Assignment # 1Power Point Presentations1. 1.8_Radiation.2. 1.9_First Law of Thermodynamics. Heat &

Work.3. 2.13_Mirror formula.4. 2.14_Determination of focal length of a

concave mirror.5. 2.21_Lens Formula.

15

Assessments Cont’d:

Group Assignment # 2:Power Point Presentations1. 2.24_Sound Waves.2. 2.25_Determining the velocity of sound.3. 3.12_Applications in the Aerofoil4. 3.13_Surface Tension.5. 3.13_Capillarity.

16

Assessments Cont’d:

Tutorial Groups are Assignment Groups:

1. Mondays – 12:15 p.m. (Mechanical Eng.)2. Tuesday s– 10:15 a.m. (Civil Eng.) 3. Tuesdays – 2:15 p.m. (Civil Eng.)4. Wednesdays – 2:15 p.m. (Civil Eng.)5. Thursdays – 2:15 p.m. (Civil Eng.)

NB: Two (2) groups present in a week.

17

Assessments Cont’d:

Categories of Assessment (Oral Presentation)

1. Lucidity (Clear, easy to understand) = 5 marks

2. Coherence = 5 marks3. Organization & Use of Aides = 5 marks4. Interest generated & Use of time = 5 marks5. Handling of Lecturer's question = 5 marks6. Written Report = 25 marks

Total = 50 marks

18

1.1 Intro. & Concept of Temp. Cont’d

Types of Temperature Scales:Kelvin/Thermodynamic: Unlike the Celsius, changes in thermometric property are directly proportional to temperature changes.

Fixed pts: Absolute Zero and Triple point of H2O

Absolute Zero: Temperature where molecular vibrations of matter stops.

Triple point of water: Temperature where pure water in all three phases coexist in equilibrium at 600 Pa (4.58 mm Hg).

TX

19

1.1 Intro. & Concept of Temp. Cont’d

Kelvin Temperature:

(A- Level Physics by Roger Muncaster, 4th Ed., pp 260-1.

KXXXXT

abszeroTrpt

abszeroT 16.273

Value of Thermometric property at absolute zero, triple point and the unknown thermodynamic/Kelvin temperature.

TTrptabs XXX ,,

20

1.1 Intro. & Concept of Temp. Cont’d

Conversions between Temperature Scales:

Celsius and Kelvin:

15.2730CK

T

(A- Level Physics by Roger Muncaster, 4th Ed., pp 261.

Celsius and Fahrenheit: FC

F 00 328.1

21

1.2 Measurement of Heat & Thermometers

Temperature Celcius (0C) Fahrenheit (0F)

Kelvin K

Sun’s surface 5500 9900 5800Tungsten melts 3422 6192 3695Lead melts 327.5 621.5 600.6Water boils 100 212 373.2Human body 37.0 98.6 310.2Room 22 72 295Water freezes 0 32 273Dry ice (CO2) -78.5 -109.3 194.7Liquid Nitrogen -198.8 -325.8 74.4Liquid Helium -268.9 -452.1 4.2Absolute Zero -273 -459.7 0

22

1.2 Measurement of Heat & Thermometers

Temperature:It is measure of how hot or cold a body is.

Heat:It is the transfer of energy solely on the

account of a temperature difference.

23

1.2 Measurement of Heat & Thermometers

Introduction:Heat in physics, transfer of energy from one part of a substance to another, or from one body to another by virtue of a difference in temperature. Heat is energy in transit; it always flows from a substance at a higher temperature to the substance at a lower temperature, raising the temperature of the latter and lowering that of the former substance, provided the volume of the bodies remains constant. Heat does not flow from a lower to a higher temperature unless another form of energy transfer, work, is also present. Microsoft ® Encarta ® 2007

24

1.2 Measurement of Heat & Thermometers

Heat:It is the transfer of thermal energy solely on the account of a temperature difference. The magnitude of the heat that is transferred is dependent on:

1. Mass of object2. Temperature difference3. Nature of the object

mcQ

25

1.2 Measurement of Heat & Thermometers

Calorimetry:It is study of heat exchanges using a device called the calorimeter. They are various methods employed in calorimetry namely:

1. Method of Mixtures.2. Electrical Method3. Continuous Flow Method4. Method of Cooling5. Mechanical Method

26

1.2 Measurement of Heat & Thermometers

Types of Thermometers:

(Advanced Level Physics through diagrams by Stephen Pople , pg 71.

27

1.2 Measurement of Heat & Thermometers

Types of Thermometers Cont’d:

(Advanced Level Physics through diagrams by Stephen Pople , pg 71.

28

1.2 Measurement of Heat & Thermometers

Types of Thermometers Cont’d:

(Advanced Level Physics through diagrams by Stephen Pople , pg 71.

29

END OF LECTURE