How does fusion not violate basic principles it must loose energy somewhere (input e > output e)?

Question

If the useable energy of a system must decrease then how will fusion satisfy our energy needs? Somewhere in the system more energy must be required than is generated from the system. I am thinking fusion energy may not be the saviour we expect it to be.

Answer 1

Both fusion and fission make use of the fact that if you dissassemble a bunch of given atoms of a given element and recombine the parts to form a bunch of atoms of a different element, the new atoms have a different "binding energy" (see ref. 1). The binding energy is a measure of how hard it is to take an atom apart (i.e., how stable it is). If the binding energy of the new atoms is less than that of the given atoms, you must input energy to do the recombination, but if it is greater, you get energy output. Fusion produces heavier elements and fission produces lighter ones, and they both tend to converge on an atomic number of 56, iron, where neither fusion of fission is possible. Thus you get power from either fusion or fission because of the fact that the fuel atoms are less stable; they haven't reached their maximum binding energy. A detailed graph of binding energies of various element isotopes is shown in ref. 2.

Answer 2

The extra energy comes (or will come) from developing a limited chain reaction. Consider a hydrogen (fusion) bomb. The release of energy is far greater than the input energy because, once a threshold is reached, a chain reaction occurs that causes other particles to fuse. The problem is, there is a minimum mass (called a critical mass) involved in creating an H-Bomb. If the mass in the bomb is below the critical mass, a chain-reaction resulting in an explosion will not occur. If you have at least the critical mass you get a large, uncontrollable explosion. The trick of using fusion as a power source is to cause a limited chain-reaction using an amount of fusible material that's FAR below the critical mass - and, therefore, controllable.

Answer 3

It comes back to Einstein's e=mc^2. In fusion, you convert a small amount of mass, m, into energy, e. The speed of light, c, (186000 miles/sec) is a large number, so when you square it, you see that you get a tremendous amount of energy if you can convert a small amount of mass. It doesn't violate any basic principles because it's not destroying matter or creating energy. It's just converting between them.

I should mention that current research into fusion reactors has been unable to break even on energy. At the moment, the reactors all consume far more energy than they produce. We'll see if someone is able to figure out a way to do it. In the meantime, conserve energy, and look into wind or solar.

Answer 4

Fusion releases some of the binding energy of the nucleus.

Basically, helium is the most tightly bound and stable nucleus of all - fusing other nuclei together to make it will release some of their energy.

The lower binding energy is visible as a lower mass.

Answer 5

fusion reaction is goverened bt Einstein equation

E = mc^2

in fussion the mass of the atoms or particals combining is more than the mass of the resultant atoms or particals so a large amount of energy is released.

Answer 6

It draws energy from somewhere else. Plus, energy isnt exactly constant, matter can be turned into energy and energy can be turned into matter.

Answer 7

Matt is right. If x > 0 then ln(-x) = ln(x) + i*pi, so interior the expression ln(-e) - ln(-a million/e), the imaginary factors will cancel. EDIT: This assumes that we chosen the vital branch of the organic logarithm. If we view the organic logarithm as a multivalued function then ksoileau's answer is right. reaction: ln(a million/x) = -ln(x) is valid whilst x > 0, yet could fail for different values of x, if we choose a vital branch of the organic logarithm. case in point, ln(a million/(-a million)) = ln(-a million) = pi*i. a similar difficulty arises with sq. roots of unfavourable numbers. you will have seen here "info": a million = sqrt(a million) = sqrt((-a million)*(-a million)) = sqrt(-a million) * sqrt(-a million) = i * i = -a million