ENERGY
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ENERGY UNITS
 Energy: The ability to do work (make something happen)
 Joule (J)
 Calorie (cal)
 The calories on food packages are really kcal
 Electron Volt (eV)
 British Thermal Unit (btu)
 Kilo watt hours (kW·h)
1 cal
4.184 J
1 eV
1.620×10-19 J
1 btu
1055 J
1 kW·h
3.600×106 J
 Your body gets 8,000 J (1900cal=1 .9kcal ) of energy from eating a
peanut.
 60 J of energy are needed per second to keep a 60 W bulb lit
 1 gallon of gas produces 1 .32 ×10 8 J of energy or enough energy to
light a 60 W bulb for 25 days.
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WORK
 Work (J)
 Work is always a change in energy. How much energy it took
to do ____________.
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POWER
 Power ( 𝑤𝑎𝑡𝑡
𝐽
𝑠
energy per time)
 Mechanical Power
Appliance
 𝑃 =𝐹×𝑣
𝑚
𝑠2
 F = Force (weight 𝐹 = 𝑚𝑔 g=9.8 )
 v = velocity
 Electrical Power
 𝑃 =𝐼×𝑉
 I = current
 V = voltage
Power
T.V.
120 W
Computer and Monitor
270 W
Washing Machine
425 W
Refrigerator
725 W
Dishwasher
1800 W
Dryer
3400 W
 The hoover dam on average produces 4.5 ×10 4 W per hour.
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http://www.energysavers.gov/your_home/appliances/index.cfm/mytopic=10040
T YPES OF ENERGY
Potential
Kinetic
 Gravitational
 Stored Mechanical
 Chemical
 Nuclear
 Electrical
 Sound
 Motion
 Electrical
 Radiant
 Thermal
 Sound
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GRAVITATIONAL
P O T E N T I A L E N E R GY
 Energy from position.
 𝐸 = 𝑚𝑔ℎ
𝑚
 g=9.8 𝑠 2
 h=height
 m=mass
 Examples of gravitational energy:
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MOTION
K I N E T I C E N E R GY
 Energy from motion.
 𝐸 = 12 𝑚𝑣 2
 m=mass
 V=velocity
 Examples of motion energy:
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ENERGY TRANSFER
 Law of conservation of energy
 Energy cannot be created or destroyed
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CHEMICAL
P O T E N T I A L E N E R GY
 Energy that can be released if a chemical reaction occurs.
 Combustion
 2C 8 H 18 + 25O 2  16CO 2 + 18H 2 O
ΔH=-10,941
𝑘𝐽
𝑚𝑜𝑙
 Examples of chemical energy:
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STORED MECHANICAL
P O T E N T I A L E N E R GY
 Energy stored in object by tension.
 Spring
 𝐸 = 12 𝑘𝑥 2
 K = spring constant
 x = distance from at rest position
 Stretched rubber band
 Examples of stored mechanical energy:
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NUCLEAR
P O T E N T I A L E N E R GY
 The energy stored inside the nucleus of an atom.
 𝑝𝑚 𝑝 + 𝑛𝑚 𝑛 ≠ 𝑚 𝑛𝑢𝑐𝑙𝑢𝑠
 𝐸 = 𝑚𝑐 2
 m = mass
 c = speed of light 3.00×10 8 𝑚𝑠
Fission
 Examples of nuclear energy
 Fission (Breaking atoms apart)

235
92 𝑈
+ 10 𝑛 →
141
56 𝐵𝑎
+
92
36 𝐾𝑟
+ 3 10 𝑛
 releases 3.5x10-11 J per reaction (2.1×1013 J per mole)
 Fission is what happens in nuclear reactors. Although
pollutant are produced, radio active waste is left over.
Fusion
no
 Fusion (Joining atoms together)
 6D  2 4 He + 2p + 2n
 releases 3×108 kJ per each gram D
 These are the type of reactions that go on in the sun.
 In order to get fusion to happen on earth we need to be at high temperatures
(10 8 K)
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ELECTRICAL
P O T E N T I A L O R K I N E T I C E N E R GY
 Potential
 The energy associated with the attractive force between 2 oppositely
charged particles
 𝐸=
1
4𝜋𝜀°
𝑞1 𝑞2
𝑟12
2
𝐶
 ε˚= vacuum permittivity 8.85 × 10−12 𝐽∙𝑚
 q = charge
 r = separation
 Kinetic
 The energy generated from the flow of electrical change (electrons)
 𝐸 = 𝑉𝐼𝑡
 V = voltage
 I = current
 t = time
 Examples of electrical energy:
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RADIANT
K I N E T I C E N E R GY
 The energy in electromagnetic waves.
 𝐸 = ℎ𝜈
 h plank’s constant 6.626×10 -34 J·s
 Frequency 𝜈 =
𝑐
𝜆
 c speed of light 3.00×108𝑚𝑠
 λ wavelength

Examples of radiant energy:
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SOUND
K I N E T I C A N D P O T E N T I A L E N E R GY
 The energy that is moved through substances with
longitudinal waves.
𝐸=
𝑎2𝜌
2𝜋𝑓
(E in this expression is energy density or energy per area)
 a = particle acceleration
 ρ = air density
 f = frequency of sound
 Examples of sound energy:
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THERMAL
K I N E T I C E N E R GY
 Energy that is caused by heat.
 When thermal energy is applied atoms/molecules move faster.
 𝐸 = 𝑓 12 𝑘𝑇
 f = degrees of freedom
 k = Boltzmann’s constant 1.381×10 -23
𝐽
𝐾
 T = temperature
T=Cold
T=Hot
 Examples of thermal energy:
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T YPES OF ENERGY
Potential
Kinetic
 Gravitational
 Stored Mechanical
 Chemical
 Nuclear
 Electrical
 Sound
 Motion
 Electrical
 Radiant
 Thermal
 Sound
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WORLD ENERGY
2014
Source of Energy
Percent
Petroleum
32%
Natural Gas
24%
Coal
30%
Renewable
10%
Nuclear
4%
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WORLD ENERGY
2014
Country
China
United States
Russia
India
Japan
Canada
Brazil
Germany
Korea, South
Iran
Energy Consumption
(Quadrillion Btu)
Country
Energy Consumption/person
(MBtu)
119.3
98.0
30.7
24.3
18.9
14.5
12.8
12.7
11.1
10.7
Qatar
United Arad
Emirates
Netherlands
Iceland
Kuwait
Singapore
Bahrain
Canada
Norway
Saudi Arabia
United States
(#14)
1160
http://www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm?tid=44&pid=44&aid=2
800
750
687
635
633
614
427
407
398
314
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US ENERGY
US Sources of Energy 2014
(Quadrillion Btu)
http://www.eia.gov/totalenergy/data/monthly/
Source
of
Energy
%
World
2014
%
US
2014
%
US
2009
Petroleum
32%
35%
37%
Natural Gas
24%
28%
25%
Coal
30%
18%
21%
Renewable
10%
10%
8%
Nuclear
4%
8%
9%
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SOUTHERN CA EDISON
If you are interested in the energy use of
buildings at UCSB you can find this
information on the interactive UCSB map
http://energy.ucsb.edu/gaucho_monitor.html
http://newsroom.edison.com/stories/sce-increases-its-total-renewable-energy-sources
Source
of
Energy
%
Edison
2012
%
US
2012
Natural Gas
42%
26%
Coal
9%
42%
Renewable
39%
12%
Nuclear
9%
19%
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ELECTRICIT Y
 Voltage (volt V): A measure of
its electrical potential .
 Which water tower will have
water that comes out at a
greater pressure?
 What represents voltage?
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ELECTRICIT Y
 Current (amps A): The rate of
charge flow per time .
 Which water tower will have water
come out at a faster rate?
 What represents current?
 Types of Current:
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ELECTRICIT Y
 Resistance (ohms Ω): The amount of
resistance a current will encounter.
 Which water tower will have the
water encounter more resistance?
 What represents resistance?
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ELECTROMAGNETS
 A changing magnetic field induces a electric field.
 A changing electric field induces a magnetic field.
 Electromagnet: A temporary magnet whose ef fect is caused
by an electric current.
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ELECTROMAGNETS
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 The University of Colorado has computer simulations for
dif ferent science concepts. Try this one on generators.
http://phet.colorado.edu/en/simulation/generator
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 Transformer: An electrical device by which alternating current
of one voltage is changed to another voltage.
 The greater the number of coils the greater the voltage.
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