Why the Fusion reaction takes place at high temperature among the nuclei, though these experience repulsion between them:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Kinetic energy is high enough to overcome repulsion between nuclei
For fusion two nuclei must come close enough for the short-range attractive nuclear force to act. Both are positively charged, so they first have to climb the Coulomb barrier. At a very high temperature the nuclei have a large average kinetic energy, \( \frac{3}{2}kT \), which lets them overcome this repulsion and get close.
NCERT (2026-27):
Nuclear Fusion – Energy Generation in Stars – “… For fusion to take place, the two nuclei must come close enough so that attractive short-range nuclear force is able to affect them. However, since they are both positively charged particles, they experience coulomb repulsion. They, therefore, must have enough energy to overcome this coulomb barrier. … When fusion is achieved by raising the temperature of the system so that particles have enough kinetic energy to overcome the coulomb repulsive behaviour, it is called thermonuclear fusion.”