combining two nuclei together requires high temperatures to
A remove the electrons which surround the nuclei
B overcome the electric repulsion of the nuclei
C make sure the nuclei thoroughly mix when they collide
D force the nuclei to expand
fusion reactions require very high temperatures because
A large amounts of energy are used up in the reaction
B the chemical bonds must first be broken
C the electrons must be stripped from the atoms
D the electric repulsion of the nuclei must be overcome
which of the following statements about the energy generating process in o sun is true?
A it can be duplicated efficiently on Earth with our present technology
B mass is converted to energy
C hydrogen becomes helium in one step
D we have detected many more neutrinos from the process than we expected to find
the energy released when one pound of fuel is "fused" is roughly equal to the energy released in the reaction of
A 10,000 pounds of TNT
B 1 pound of uranium
C 10 pounds of uranium
D 1 ton of uranium
the reactions which usually produce the energy of stars are
A chemical reactions
B fission reactions
C fusion reactions
D reactions unknown on the Earth
fusion is an unusable source of commercial energy today because of
A the expense involved
B the high temperatures required
C the lack of available fuel
D the vested interests of the oil companies
a fusion reaction results in
A the breaking apart of a nucleus
B the building up of heavier nuclei from lighter ones
C the complete annihilation of nuclei
D the creation of neutrons
large fusion reactors are undesirable because
A large amounts of radioactive waste products are also produced
B large amounts of fuel are needed
C large amounts of heat must be dissipated
D all of these
which of the following statements about the energy-generating process in the sun is true
A it can be duplicated efficiently on Earth with our present technology
B some mass is converted to energy
C hydrogen becomes helium in a single step
D the forces involved are all electromagnetic
the reactions which require the greatest temperature are the
A proton-proton chain
B triple alpha process
C carbon cycle
D uranium fission
the energy released in one fusion reaction is roughly equal to the energy released in
A one chemical reaction of TNT
B 10,000 chemical reactions of TNT
C one fission reaction
D 10,000 fission reactions
which of the following is true in the proton-proton chain?
A protons are fused to produce deuterium or heavy hydrogen.
B protons are split to form neutrons and positrons.
C protons produce helium directly.
D protons decay into energy and neutrinos.
high temperatures are required for fusion reactions because high velocities
A are needed to penetrate the electrons which surround the nuclei
B are needed to overcome the electric repulsion of the nuclei
C are needed to crack the surface of the nuclei
D lead to release of greater amounts of energy per reaction
fusion reactions require very high temperatures because
A the atoms must first be broken apart by violent collisions
B the electric repulsion of the nuclei must be overcome
C many reactions must occur before significant results are obtained
D the necessary elements do not exist at low temperatures
the main nuclear reactions that keep our sun shining begin with which building blocks?
A three carbon nuclei
B two electrons
C two hydrogen nuclei
D a deuteron and a positron
fusion reactions are a likely source of energy for stars because
A the amount of fuel available is larger
B the energy released in a reaction is large
C the temperature is large
D all of the above
the heaviest element that can be created in normal nucleosynthesis is
A iron.
B helium.
C uranium.
D carbon.
E bagelium.
fusion reactions release energy by
A converting mass into energy
B releasing internal forms of energy
C giving off high energy fragments
D creating simpler forms of matter
according to present ideas, the sun produces energy primarily by
A gravitational collapse.
B nuclear fission.
C cno cycle.
D triple-alpha process.
E proton-proton reactions.
pound for pound what source releases the greatest amount of energy in a typical star
A fusion
B fission
C chemical reactions
D gravity?
the reactions currently going on in the sun are the
A proton-proton chain
B triple alpha process
C carbon cycle
D boron fission
fusion reactions occur (not counting still unconfirmed news)
A spontaneously whenever the appropriate fuel is present
B only when the fuel is heated to very high temperatures
C only when the fuel is compressed to very high densities
D whenever the fuel is stimulated by an appropriate fragment from another fusion reaction
the principal source of energy generation in the sun is
A the conversion of hydrogen to helium
B the conversion of helium to carbon
C the conversion of helium to hydrogen
D gravitational contraction
the energy production of a star while it is on the main sequence results primarily from
A gravitational shrinking.
B nuclear fusion.
C nuclear fission.
D proton instability.
E chemical reactions.
the energy of the sun is derived from
A the conversion of helium into hydrogen
B gravitational collapse
C the decay of heavy elements
D the building up of helium from hydrogen
high temperatures are required before fusion reactions can begin in order to
A strip the electrons from the nucleus
B break the nuclei into small enough fragments to react
C overcome the electric repulsion between nuclei
D generate enough light
the particles which combine in nuclear fusion are
A electrons and protons
B neutrons and protons
C negatively charged nuclei
D positively charged nuclei
the source of the sun's energy is
A nuclear reactions
B combustion reactions
C exotic chemical reactions
D totally unknown
the proton-proton chain is most important in
A main sequence stars of high surface temperature
B main sequence stars of low surface temperature
C stars of advanced age
D white dwarf stars
which set of reactions is responsible for producing new carbon in stars
A carbon cycle
B triple alpha process
C proton-proton chain
D each of the above
which of the following reactions directly converts hydrogen into helium
A triple alpha
B proton-proton
C carbon cycle
D fission
energy can be released by the
A fission of light elements
B fusion of light elements
C fusion of heavy elements
D radioactive decay of electrons
energy is released when two protons combine because
A the resulting particle moves with very high velocity
B an explosion results which releases energy
C a third particle is destroyed in the process
D some mass is converted into energy during the reaction
a fusion reaction results from
A binding two atoms together into a molecule
B binding two nuclei into a new nucleus
C breaking apart a nucleus
D stripping the electrons off an atom
why does hydrogen fusion occur only in a star's center?
A only near the center is there enough heat and pressure.
B only near the center does enough hydrogen exist that is not mixed with other elements.
C only near the center is the speed of light favorable for the reaction to occur.
D heat is transferred down to the center during the main sequence life of the star.
E the statement is false; fusion occurs throughout the star's volume. this is what causes the
surface to be bright.
the sun's energy is generated by
A gravitational contraction.
B nuclear fission.
C hydrogen fusion.
D helium fusion.
E chemical reactions.
a hydrogen bomb requires an atomic bomb trigger because
A neutrons are necessary to form helium
B the electrons must first be stripped from the hydrogen atoms
C high temperatures are necessary to overcome the electric repulsion of the hydrogen nuclei
D no trigger is needed at all
what is special about iron-56 nuclei?
A if they are fused with other nuclei, kinetic energy is absorbed, not generated
B if a star's core becomes primarily iron-56, it can no longer generate the energy required to support itself against its own weight
C it and all nuclei with more protons are currently generated only during supernova explosions
D all of the above
four protons weigh
A more than one helium nucleus
B less than one helium nucleus
C the same as one helium nucleus
D an unknown element
the minimum temperature required for helium "burning" to start in the core of a star is
A 10 million degrees
B 100 million degrees
C 1 billion degrees
D helium burning can occur in a star's core at any temperature
if all the stars were mostly helium rather than mostly hydrogen, which of the following would be true
A the centers of stars would be cooler
B stars would never fuse anything in their centers
C the centers of stars would be hotter
D stars would evolve directly to the white dwarf stage
the theoretical limit for the buildup of elements by fusion reactions in stars is
A iron
B carbon
C uranium
D magnesium
a necessary condition for the occupance of fusion reactions in the appropriate fuel is
A critical mass
B proper catalyst
C high temperature
D free neutrons
in the h-bomb, the reaction that occurs converts
A hydrogen into helium
B helium into hydrogen
C hydrogen and helium into heavier elements
D uranium into lighter elements
the proton-proton chain and other nuclear reactions that build heavier nuclei from lighter nuclei are called:
A nuclear fission.
B nuclear fusion.
C atomic bombs.
D elemental transmutation.
the easiest element to fuse is
A hydrogen
B helium
C iron
D uranium
in fusion reactions, energy is liberated because
A some mass is converted directly to energy.
B the helium produced is more massive than the hydrogen that is fused together.
C fusion reactions occur near the sun's surface.
D hydrogen is a very hot gas.
what is inferred to be the source of the sun's energy now?
A fusion reactions in the core.
B gravitational energy released by collapse.
C shock waves produced by high-velocity gases.
D fission reactions in the core.
E oxidation of materials such as carbon.
which of the following is an important source of energy in most stars
A combustion
B fission
C fusion
D chemical
fusions have not yet been controlled in the laboratory because
A we cannot produce the necessary conditions for the reactions to begin
B we cannot produce the proper fuel
C we cannot contain the fuel during the reactions
D such control would have no desirable advantages and has not been attempted
the fundamental process which releases energy inside a star like the sun I
A nuclear fission
B nuclear fusion
C radioactive decay
D neutrino emission
in hydrogen "burning" in stars
A hydrogen unites with oxygen producing water
B four protons fuse forming the helium nucleus and liberating energy
C the "flames" are prominences seen on the limb of the sun
D helium is converted to carbon
the heaviest single atom which can be "built" by fusion, in the core of a very hot star is
A helium
B carbon
C oxygen
D iron
in the carbon cycle,
A carbon acts as a catalyst during the fusion of hydrogen into helium
B carbon is produced from helium
C the net result is that carbon is converted into heavier elements
D carbon and oxygen undergo a combustion reaction
why do hydrogen fusion reactions only occur in the deep interiors of the sun (and other stars)?
A because this is the only place in the sun where the requisite catalysts (c n, and o) exist in sufficient quantities to permit fusion to occur
B because the requisite conditions of high temperature and high density only occur there
C because only in the core is the temperature low enough and the density high enough to allow fusion to occur
D because this is the only place in the sun where there is sufficient hydrogen
the theoretical limit for the buildup of elements by fusion reactions is
A carbon
B magnesium
C iron
D uranium
according to present ideas, the sun produces energy primarily by
A gravitational collapse
B nuclear fission
C carbon cycle
D proton-proton reactions
why must the temperature be so high in order for fusion to take place?
A only at high temperatures can protons' mutual electromagnetic repulsion be overcome by the strong force of nuclear attraction
B only at high temperatures can protons' strong force mutual repulsion be overcome by the electromagnetic force of attraction
C only at high temperatures are nuclei close enough together to "stick"
D only at high temperatures will atomic nuclei split apart
the reactions which transform light nuclei to heavy nuclei are called
A fusion reactions
B fission reactions
C chemical reactions
D no choice
the reaction which produces carbon in stars is called
A the proton-proton chain
B the carbon cycle
C the triple alpha process
D fission
the building up of heavy nuclei from lighter ones is called
A radioactivity
B nuclear fusion
C nuclear fission
D spontaneous combustion
the heaviest element which can be created in energy-producing fusion reactions is
A iron
B carbon
C silicon
D uranium
the carbon cycle
A converts hydrogen to helium
B converts helium into carbon
C fuses carbon into still heavier elements
D moves carbon from the center of a star to the surface
to start nuclear burning in a star, high temperatures are required to
A overcome the nuclear force between the protons
B overcome the nuclear force between the neutrons
C overcome the electric force between the neutrons
D overcome the electric force between the protons
the set of reactions our sun goes through to convert hydrogen into helium is
A the carbon cycle
B the triple alpha process
C the neutron-neutron cycle
D the proton-proton chain
fusion, in the sun, is
A the process by which the sun contracts, converting gravitational potential energy into heat
B the conversion of protons into helium nuclei
C the conversion of helium into hydrogen with a resulting release of nuclear energy from the leftover mass
D the result of the combination of the electron clouds of one carbon atom with two oxygen
atoms, with a release of some of the stored energy
which of the following could be an energy source in a pure hydrogen star?
A the proton-proton process
B the carbon cycle
C the triple-alpha process
D radioactive decay
what is the heaviest element that the most massive stars can fuse in their cores in stable nuclear reactions?
A helium.
B oxygen.
C nitrogen.
D carbon.
E iron.
at the end of the helium "burning" process the helium nuclei have turned into a nucleus of
A carbon
B hydrogen
C beryllium
D oxygen
high temperatures are required for hydrogen fusion reactions to occur because
A high potential energy is required
B like charges repel
C neutrinos can be explained only with high temperatures
D opposite charges attract
the "trigger" of a h-bomb which initiates the fusion reactions is
A a mechanical device
B a conventional TNT explosive
C an atomic bomb
D a particle accelerator
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