Transcript Fusion - Cyberphysics

Fusion
The power source of the stars!
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What is nuclear fusion?
• Fusion is the fusing together of two
small nuclei to produce a bigger nucleus
and release energy in the process.
• It is the nuclear reaction that takes
place in the stars!
Keywords are in red
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What conditions are needed for
fusion to occur?
• High temperature
• High Pressure
• Just what you get
inside a star!
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Why does fusion happen?
• Fusion occurs only if its
product is of lower energy
(or is more stable ) than
the two nuclei that fuse
together.
• This is only the case for
nuclei with less than 56
protons… therefore
elements up to iron are
made within the normal
fusion process in a star.
• Heavier elements are made
in supernovae explosions.
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We Are stardust!
• A star is made up mainly of
hydrogen and helium. In the
early Universe hydrogen was
the only element!
• Fusion is the process by which
nuclei fuse together and
heavier nuclei are formed.
• Explosions of massive stars
result in heavier elements –
these are then flung out into
space.
• We are stardust – the atoms in
us were formed inside the great
fusion reactors out in space – or
when the explode into stardust!
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• Hydrogen nuclei are
single protons
• They fuse to give
deuterium (an
isotope of hydrogen)
and a free positron
and neutrino
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• The deuterium fuses
with another
hydrogen nucleus
forming helium 3 –
excess energy is
given out as a
photon.
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• Two of these helium3 nuclei can combine
to give the very
stable helium 4 and a
lot of energy is
released. When
something more
stable is produced
energy is given out.
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Another reaction equation
• There are more ways
in which fusion can
occur.
• A Deuterium can
combine with
tritium.
• Could you write the
equation for that?
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Another reaction equation
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The sort of questions you could
get
• Explaining what fusion is.
– Two smaller nuclei fusing into one
• Explaining what conditions are needed for the
reaction
• Recalling that the primary reaction is
hydrogen fusing to make helium but that it
then goes on to make other elements too.
• Balancing an equation that was partly filled in
for you.
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