??? I?????

1
??? I ?????
??????????????????????????,????????????????????,??
???????????????,?????????????????????????
2
??????????????????????(Sadi Carnot)????????????,??
???????????,??????????????????????????????????,???
????????????????????????????(Clausius)????????,??(
entropy)???????1865???????????
3
?????????,??????????,?????????????????????????????
???????????????,??????(kinetic theory)????????????
??????????????,??????????????(statistical
mechanism)?
4
The worst common burns you can imagine are steam
burns. You have not only water heated to its
boiling point but gaseous steam carrying the heat
of vaporization. Its a great deal of energy in
a small space.
5
???????
???C???A?B???????(??????,????A?B??????),????A?B?
???????(????),???????????,????A?B????????????(Sugg
ested by Ralph Fowler,1931)
6
??
??????????????? ??????????????????????? ???????(
????????)??????? ?????????????? ????????????????
??
7
????(????)
8
Measuring temperature

• The measure of temperature is a way of expressing
  how much heat one object is holding relative to
  another.
• There are several examples shown at right. You
  can base a thermometer on thermal expansion of a
  gas, differential expansion of bimetal strips,
  even on something as wild as laser-doppler shift.

H.W. Find the principle three thermometer
9
Conversions are expected

• Values on the temperatures scales (Fahrenheit,
  Centigrade/Celsius, and Kelvin) may be readily
  interconverted. Physics professors will want
  values to eventually be in Kelvins because thats
  the form in SI units..

10
Thermal expansionlinear

• A change in length will accompany a change in
  temperature. The size of the change will depend
  on the material.

11
17.4 Thermal Expansion
12
Coefficients of expansion
13
Thermal Expansion

• Water is interesting. There are no other liquids
  that expand to become less dense as a solid than
  they are as a liquid. This is fortunate, if lakes
  were to freeze and dense ice sink to the bottom,
  everything in the water would die as the liquid
  became solid from the bottom up.
• Thermal expansion joints allow roads to expand
  and contract without any stress to the material
  used to build.

H.W. Find the minimum gap size required when
building a bridge
14
James Joule and the mechanical equivalent of heat

• Joule knew a mass above the ground had potential
  energy. He dropped an object on a cord, turning a
  paddle in water monitored by a very accurate
  thermometer.
• His conclusion was to connect energy conservation
  (potential and kinetic) to heat as a third form
  observed.

15
Thermal Stress
16
If a steel is confined to a strictly fixed
length, estimate the pressure increase per degree
temperature increase

• 2.4103 B. 2.4104 C. 2.4105
• D. 2.4106 E. 2.4107 P a

17
?(Heat) ?????,?????????????????????(?????),????
?????????,??????????
18
Specific heat values
19
Mechanisms of Heat Transfer
heat current in conduction
Thermal conductivity
20
???????????2??,??????0.8??????????1kg??,???????30?
,??????????????? (??????334kJ/kg)

• 2 B. 4
• C. 6 D. 8
• E. 10 Hr

21
Why is it a good reason not to pick up a metal
frying pan by its bare handle?
How about a metal frying pan with a wooden handle?

1. Wood B. Copper C. same

22
????(Convection)
????????????
23
Radiation
Heat current in radiation
Stefan-Boltzmann constant
The net rate of radiation from a body
24
The Rattlesnake