# Homework Help: Proton proton cycle

1. Sep 17, 2011

### logearav

1. The problem statement, all variables and given/known data

Dear members,
In proton proton cycle, Two protons fuse together to form a duetron with positron and nuetrino.
Then duetron combine with another proton to form 2He3, which then combines with another 2He3 to give 2He4
The final reaction is
41H1+2e---> 2He4

2. Relevant equations

3. The attempt at a solution
Only three protons fuse together in the process, then how in the final equation it has been stated 4 protons fuse. For 2He3 to combine with 2He3 , the reaction of proton fusing with another proton, giving duetron, which fusing with another proton, should happen twice. So it is 6 protons fusing. So why its been mentioned only 4 protons fuse to form helium. Please help revered members
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Sep 17, 2011

### Redbelly98

Staff Emeritus

6 protons fuse to form 2 helium-3 nuclei. Then the two helium-3 nuclei form helium-4 plus 2 protons.

Alternatively, you might write a net reaction that doesn't include 2 of the original 6 protons -- in which case you wouldn't have the 2 protons that are left over in the end.

3. Sep 17, 2011

### logearav

6 protons fuse to form 2 helium-3 nuclei. Then the two helium-3 nuclei form helium-4 plus 2 protons.

Thanks for the reply sir. But i didnt understand the lines quoted above.

4. Sep 18, 2011

### Redbelly98

Staff Emeritus
Is this a homework problem? I am having trouble understanding exactly what the problem is asking, or whether you are just trying to understand for yourself what happens in nuclear fusion.

5. Sep 18, 2011

### logearav

Sir, i am asking to get clarified, because my teacher has not given satisfactory reply. I got 90% of what you said, but i cant understand the lines you have written which i quoted in my previous query.
Thanks again. This is the forum which gives excellent insights to physics, thats why i keep raising my query

6. Sep 20, 2011

### Redbelly98

Staff Emeritus
Okay, so omit the intermediate products (He-3 nuclei) and write that as
6 1H → 4He + 2 1H (+ energy, positrons, and neutrinos)
We have hydrogen nuclei on both sides of the reaction, so we can take away 21H from each side. That leaves us with the net reaction.

7. Sep 21, 2011

### logearav

Mr.Redbelly, Fantastic. I got it now. Thank you so much, sir