What types of energy are there?
• Nuclear
• Fusion
• Fission
• Mechanical (Kinetic)
• Potential
• Gravity
• Springs
• Chemical
• Light
• Heat
• Electrical

The solar surface
Fusion 7

The sun flare 
The corona during an eclipse  The aurora
Fusion 8

• Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus.
• It is accompanied by the release or absorption of energy depending on the masses of the nuclei involved ..

The Sun derives energy from fusion of protons. There are many possibilities, but two detailed cycles were proposed.
The hydrogen cycle:
2
H + H  2 D (+e – ) +  + + n
D + H  3 He + 
3 He + 3 He  4 He + 2 H net
4 H = 4 He (+ 2e
–
) + 2
 + + 2
 + 2 n + 26.7 MeV
Or
Enough energy to keep a 60W light bulb on for 7 x 10 -14 sec
Fusion 10

E = mc 2
1 H, 2 D
3 T, 4 He
Stars are giant fusion reactors.
Nuclear fusion reactions provide energy in the Sun and other stars. Solar energy drives the weather and makes plants grow.
Energy stored in plants sustains animal lives, ours included.
11 Fusion

Sun Mass is 333,000 times that of the Earth.
The sun is a big nuclear fusion reactor, 75% H and 25% He.
Sun radius (695000 km) is 109 times that of the Earth (6.4e3 km).
Sun emits 3.86
 10 26 watts, ~ 8 kwatt/cm 2 , 1.4 kwatt/m 2 reach the
Earth’s atmosphere (solar constant).
1 kwatt/m 2 reaches the Earth’s surface
This is the energy that drives our weather.
Fusion 12

Matter and Energy

We have been taught that “matter and energy cannot be created nor destroyed”
 We now need to understand that Matter and
Energy are two forms of the same thing

E = mc 2
 Matter can be changed into Energy

Einstein’s formula above tells us how the change occurs
 In the equation above:
E = Energy m = Mass c = Speed of Light (Universal Constant)
Energy Mass
Light
Speed

E = mc 2
 The equation may be read as follows:
Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squared
 This tells us that a small amount of mass can be converted into a very large amount of energy because the speed of light (c) is an extremely large number

Fusion
 Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger, heavier nucleus
 The fusion process generates tremendous amounts of energy; refer back to Einstein’s equation
 For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together

Fusion
 Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars
 The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions
 The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy

Review
 Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc 2 )
 Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei
 Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus

Tsar 2
The Russian Tsar H-
Bomb was the most powerful ever made
Fusion
Nov. 1, 1952, the first Hbomb Mike tested, mushroom cloud was 8 miles across and 27 miles high;the canopy was 100 miles wide,
80 million tons of earth was vaporized.
H-bomb exploded Mar. 1,
1954 at Bikini Atoll yielded 15 megatons and had a fireball 4 miles in diameter.
megatons.

Humans had controlled fission chain reactions before testing bombs.
1952, Nov. 1. US tested the first H-bomb at Enewetak, controlled sustained fusion reactor has yet to be achieved.
High temperature and high particle density for long period of time are the conditions for fusion.
This has not yet been achieved in a context where more energy is produced than it costs to make the reaction happen
20 Fusion

Fission
 Fission may be defined as the process of splitting an atomic nucleus into fission fragments
 The fission fragments are generally in the form of smaller atomic nuclei and neutrons
 Large amounts of energy are produced by the fission process

Fission
 Fissile nuclei are generally heavy atoms with large numbers of nucleons
 The nuclei of such heavy atoms are struck by neutrons initiating the fission process
 Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms

Fission
 A classic example of a fission reaction is that of
U-235:
U-235 + 1 Neutron
2 Neutrons + Kr-92 + Ba-142 + Energy
 In this example, a stray neutron strikes an atom of U-235.
It absorbs the neutron and becomes an unstable atom of
U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.

Fission
 The fission process is an a natural one as a
French researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to be over 2 billion years old
 Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity

Review
 Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc 2 )
 Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei
 Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus

Quiz
 Which nuclear process produces large amounts of energy?
A. Fission
B. Fusion
C. Both fission & fusion
D. Neither fission nor fusion

Quiz
 Fission is the process that _________ atomic nuclei.
A. Combines
B. Burns up
C. Stores
D. Splits

Quiz
 Mass may be converted into energy.
A. True
B. False

Quiz
 The fission process requires heavy atomic nuclei.
A. True
B. False

Quiz
 Name a nuclear reaction that occurs within the sun:

Quiz
 Fission is a natural process that occurs on the planet Earth.
A. True
B. False

Quiz
 Explain this equation:
E = mc 2