Nuclear Fusion MCQ - Practice Questions with Answers

Nuclear fusion-

In nuclear fusion, two (or) more than two lighter nuclei combine/fuse to form a larger nucleus. In this process energy is released.

Some examples of nuclear fusion:

$$
{ }_1^1 \mathrm{H}+{ }_1^1 \mathrm{H} \rightarrow{ }_1^2 \mathrm{H}+\mathrm{e}^{-}+\mathrm{v}+0.42 \mathrm{MeV}
$$

Here two protons combine to form a deuteron and a positron releasing 0.42 MeV of energy.

$$
{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H} \rightarrow{ }_2^3 \mathrm{He}+\mathrm{n}+3.27 \mathrm{MeV}
$$

Here two deuterons combine to form the light isotope of Helium releasing 3.27 MeV of energy.

$$
{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H} \rightarrow{ }_1^3 \mathrm{H}+{ }_1^1 \mathrm{H}+4.03 \mathrm{MeV}
$$
 

                            In this case, two deuterons combine to form a triton and a proton releasing 4.03 MeV of energy.

Here mass of single nucleaus so formed is less than the sum of the mass of the parent nuclei. And this mass difference appears in the form of release of energy. 

Condition required for Nuclear fusion -

The fusion to take, two nulei must come close enough so that attractive short range nuclear force is able to affect them. But since both are positively charged particles, they experience coulombic repulsion. Therefore they muct have enough energy to overcome this repulsion. For this, high pressure of 10⁶ atm & temperature of 10⁹ K is required. 

When the fusion is achieved by raising the temperature of the system, so that particle have enough kinetic energy to overcome the coulombic repulsion, it is called thermo-nuclear fusion.