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University of Guyana Faculty of Natural Sciences Depart. of Math, PHYs &amp; Stats PHY 110 – Physics FOR ENGINEERS Lecture 2 (FRIDAY, SEPT. 2, 2011). 1.1 Intro. &amp; Concept of Temperature. Introduction:

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University of Guyana

Faculty of Natural Sciences

Depart. of Math, PHYs & Stats

PHY 110 – Physics FOR ENGINEERS

Lecture 2

(FRIDAY, SEPT. 2, 2011)

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)

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)

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.

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.)

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.

1.1 Intro. & Concept of Temp. Cont’d

Historical Perspective

One 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.

1.1 Intro. & Concept of Temp. Cont’d

Historical Perspective Cont’d

In 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 .

1.1 Intro. & Concept of Temp. Cont’d

Temperature Scales:

This is a standard used in the determination of temperature.

Construction of Temperature Scale:

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

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

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

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.

1.1 Intro. & Concept of Temp. Cont’d

Celsius Temperature:

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

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

University of Guyana

Faculty of Natural Sciences

Depart. of Math, PHYs & Stats

PHY 110 – Physics FOR ENGINEERS

Lecture 2

(THURSDAY, SEPT. 8, 2011)

Assessments:

Assignments – 10%:

1. Individual: Two (2) Oral Quizz - 5%

Heat – 2.5 %

Properties of Matter – 2.5%

2. Group: Power-Point Presentation - 5%

Written Report – 2.5 %

Oral Presentation (15 min.) – 2.5 %

Topics based on the course outline.

Each Tutorial group conducts two (2) presentations.

Assessments Cont’d:

Group Assignment # 1

Power Point Presentations

1.9_First Law of Thermodynamics. Heat & Work.

2.13_Mirror formula.

2.14_Determination of focal length of a concave mirror.

2.21_Lens Formula.

Assessments Cont’d:

Group Assignment # 2:

Power Point Presentations

2.24_Sound Waves.

2.25_Determining the velocity of sound.

3.12_Applications in the Aerofoil

3.13_Surface Tension.

3.13_Capillarity.

Assessments Cont’d:

Tutorial Groups are Assignment Groups:

Mondays – 12:15 p.m. (Mechanical Eng.)

Tuesday s– 10:15 a.m. (Civil Eng.)

Tuesdays – 2:15 p.m. (Civil Eng.)

Wednesdays – 2:15 p.m. (Civil Eng.)

Thursdays – 2:15 p.m. (Civil Eng.)

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

Assessments Cont’d:

Categories of Assessment (Oral Presentation)

Lucidity (Clear, easy to understand) = 5 marks

Coherence = 5 marks

Organization & Use of Aides = 5 marks

Interest generated & Use of time = 5 marks

Handling of Lecturer's question = 5 marks

Written Report = 25 marks

Total = 50 marks

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).

1.1 Intro. & Concept of Temp. Cont’d

Kelvin Temperature:

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

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

1.1 Intro. & Concept of Temp. Cont’d

Conversions between Temperature Scales:

Celsius and Kelvin:

Celsius and Fahrenheit:

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

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.

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

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:

Mass of object

Temperature difference

Nature of the object

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:

Method of Mixtures.

Electrical Method

Continuous Flow Method

Method of Cooling

Mechanical Method

1.2 Measurement of Heat & Thermometers

Types of Thermometers:

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

1.2 Measurement of Heat & Thermometers

Types of Thermometers Cont’d:

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

1.2 Measurement of Heat & Thermometers

Types of Thermometers Cont’d:

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

END OF

LECTURE