Is the energy required for fission equal to that for fusion?

In summary: That's the energy per nucleon. The fission energy of 1 atom of Uranium is about 200 MeV, more than 10 times the energy of any fusion reaction with hydrogen isotopes.It is not really clear which processes you want to compare.
  • #1
letsfailsafe
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Hi, this is my second year studying physics and few weeks ago we went into nuclear physics very briefly because we are learning it next year.

I'm not sure if the energy required to fission is equal to the energy required to fusion. For example is energy required to fission hydrogen atom, equal to fusion particles together to create hydrogen atom? (If fissioning result particles were same with fusioning particles)

According to my friend who studies chemistry says it's not equal. (I do not study chemistry). Just according to E=mc2 if result of fission particles and particles required to fusion were the same, this means that mass and number of particles needed to fuse would be equal.

I know that fusion is much harder to do, and we can't just put particles together to form an atom... Please give me a understandable answer.
 
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  • #2
"e= mc^2" has nothing to do with the energy required to cause fission or fusion. It is, rather, the energy you get out of fusion and fission. For example, Uranium 239 fissions into Neptunium 239 plus a neutron. The total mass of the the Neptunium 239 atom and the neutron is slightly less than the mass of a Uranium 239 atom. The difference in mass turns into energy, e= mc^2, and is sent off as a gamma ray.

When two heavy hydrogen atoms combine to form a helium atom, the helium atom has slightly less mass that the total of the two hydrogen atoms. The difference in mass turns into energy.

But the energy from one atom of Uranium fissioning is NOT the same as the energy from two hydrogen atoms fusioning. The fusion energy is about three to four times greater than the fission energy.
 
  • #3
HallsofIvy said:
But the energy from one atom of Uranium fissioning is NOT the same as the energy from two hydrogen atoms fusioning. The fusion energy is about three to four times greater than the fission energy.

That's the energy per nucleon. The fission energy of 1 atom of Uranium is about 200 MeV, more than 10 times the energy of any fusion reaction with hydrogen isotopes.
 
  • #4
It is not really clear which processes you want to compare.

A specific fusion process will always release/need exactly the energy the corresponding fission process will need/release.
You can fuse deuterium+tritium (both are hydrogen isotopes) to helium+neutron, for example, this releases 17.6 MeV of energy. If you try to fission that helium nucleus again, you have to add a neutron and those 17.6 MeV of energy to get deuterium+tritium.

Fusion of light elements (like hydrogen) gives more energy per mass than fission of heavy elements (like uranium), but that is comparing apples and oranges.

For example is energy required to fission hydrogen atom
Most hydrogen atoms are a single proton, you cannot fission them.
letsfailsafe said:
I know that fusion is much harder to do, and we can't just put particles together to form an atom...
That is "just" an engineering issue.
 
  • #5
letsfailsafe said:
Hi, this is my second year studying physics and few weeks ago we went into nuclear physics very briefly because we are learning it next year.

I'm not sure if the energy required to fission is equal to the energy required to fusion. For example is energy required to fission hydrogen atom, equal to fusion particles together to create hydrogen atom? (If fissioning result particles were same with fusioning particles)

According to my friend who studies chemistry says it's not equal. (I do not study chemistry). Just according to E=mc2 if result of fission particles and particles required to fusion were the same, this means that mass and number of particles needed to fuse would be equal.

I know that fusion is much harder to do, and we can't just put particles together to form an atom... Please give me a understandable answer.

Two hydrogen atoms fusing to make a helium atom release X amount of energy. The helium atom splitting into two hydrogens absorbs that same amount of energy. The magnitude (absolute value) of the energy is the same but the sign is opposite. So they aren't equal.

The equilibrium favors helium so strongly that the reverse reaction virtually never happens and is always neglected.
 

What is the meaning of E=mc^2?

E=mc^2 is an equation that represents the relationship between energy (E), mass (m), and the speed of light (c). It states that energy and mass are interchangeable and can be converted into one another.

What is fission and fusion?

Fission and fusion are two types of nuclear reactions. Fission is the splitting of a large nucleus into smaller nuclei, releasing a large amount of energy. Fusion is the combining of two smaller nuclei into a larger nucleus, also releasing a significant amount of energy.

What is the significance of E=mc^2 in fission and fusion reactions?

E=mc^2 plays a crucial role in fission and fusion reactions as it explains the relationship between mass and energy. In fission, some of the mass of the nucleus is converted into energy according to this equation. In fusion, the combination of smaller nuclei results in a decrease in mass and an increase in energy, again in accordance with E=mc^2.

Can E=mc^2 be applied to all types of energy?

E=mc^2 can be applied to any form of energy, as all energy can be converted into mass and vice versa. However, it is most commonly used in the context of nuclear reactions and the immense amount of energy released from the conversion of mass.

How has E=mc^2 impacted the field of science?

E=mc^2 has had a profound impact on the field of science, particularly in the study of nuclear physics and energy production. It has also played a significant role in the development of nuclear weapons and has expanded our understanding of the fundamental laws of the universe.

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