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Lecture 8
Some words about diamonds (Fig. 1)
Diamonds are a form of C, which are formed under elevated temperatures and high pressures (Fig. 2).
Definition: Pressure = Force/Area
In many geologic cases pressure is the weight of the mass over a unit area
ΰ hydrologic pressure: weight of water column
ΰ lithostatic pressure: weight of rock column
Units: 1 N/m2
1 N (
Other units: 1 bar = 105 N/m2
Diamonds are found in kimberlite pipes, which represent the surface opening of deep eruptions (Fig. 3).
The measurement unit used for diamonds is Carat: 1 Carat = 200 mg; 1 point is 0.01 carat
For gold, 1 carat is the relative amount of gold present 1 carat = 1 part Au in 24.
Three forms of carbon: diamond ΰ graphite ΰ coal (Fig. 4)
Energy
Definitions
Capacity to take
action
Ability to move
matter
First law of
Thermodynamics:
Conservation of Energy:
Energy can neither be destroyed nor created.
It can be transformed from one form into another
Energy Forms
Thermal
Energy of random
movement of particles of a substance (Heat)
Mechanical
Directed
movement
Kinetic energy
of moving object
Potential energy
of position in gravity field
Electrical
Energy
associated with moving charges in electric field
Radiant
Energy of
electromagnet waves (Light)
Chemical
Energy stored in
chemical bonds
Nuclear
Energy stored in
nuclear bonds
Second Law of Thermodynamics
Three equivalent
descriptions
In any
conversion of energy, there is always a decrease in the amount of useful energy
Heat cannot by
itself flow from cold to hot; it spontaneously flows from hot to cold
The universe moves
toward the equilibrium of randomness
Examples for Efficiencies of energy conversions
Efficiency = (Energy
or work out)/(Energy or work in)
|
|
Thermal |
Mech |
Chem |
Electr |
Radiant |
|
Thermal |
|
0.45 |
|
0.08 |
|
|
Mechanical |
|
|
|
0.95 |
|
|
Chemical |
0.85 |
|
|
0.90 |
|
|
Electrical |
|
0.90 |
0.72 |
|
0.20 Fluor. 0.05 Incand. |
|
Radiant |
|
|
|
0.10 |
|
Units
Energy
Kinetic energy:
KE = ½ m v2 [kg m2/s2]
1 N = 1 kgm/s2 [N]
1 Nm = 1 J = 1
kg m2/s2 = 1 Ws
[J] Joule; [W]
Watt
Work
Work = Force x
Distance
Example: W = m h
g [kg m m/s2] = [J]
ΰEnergy and Work have identical units: 1 J = 1
Ws
Power (Capacity
to do work)
P = W/t [J/s] = W
Energy use:
Energy/Time
E/T [Ws/s]
Other expression
for energy use: kWhr/yr
ΰ Power and Energy use have identical units:
ΰ1 J/s = 1 W
Power x Time = Energy
Energy production and consumption
The big issues:
Population growth
Growth in per capita consumption
Inequality of energy consumption
Current use
Average use per person:
World 2 kW
ΰ Total use
World: 2 kW/person x 6.4 x109persons =
12.8x1012W ΰ 12.8 TW