Question

Fusion reaction takes place at very high temperature because
a) atoms are ionized at high temperature
b) molecules breakup at high temperature
c) nuclei breakup at high temperature
d) kinetic energy is high enough to overcome the repulsion between the nuclei

Answer 1

From the word fusion we can comment that it is basically two particles or n particles coming together. Fusion is a process where in two light nuclei, combine to form a single heavier nucleus. For such a process to occur the individual nuclei requires the presence of high temperature in order to absorb energy. Hence we can conclude which conditions will be favorable for fusion of two nuclei fusion from the options above.

Complete step by step answer:
Let us first understand about the nuclear fusion reaction.
This fusion reaction is a process where the two light nuclei come together and form heavy nuclei. The heavier nucleus formed has a mass lower as compared to the sum of the masses of the individual nuclei. This mass defect is released as energy according to Einstein’s mass energy relation.
The nucleus of an atom has a positive charge as the nucleus comprises protons and neutrons. The protons have a positive charge and neutrons have no charge. Hence charge on the nucleus is always positive. When two nuclei are brought close to each other there is a high electrostatic force of repulsion as the distance between the two nuclei is brought to zero. Hence high temperature is necessary for the nuclei to have sufficient kinetic energy so that they can overcome their coulombic repulsions and come closer to the range of nuclear force( force of binding that exists when two particles having the same charge are brought close to each other).
Hence the correct answer is option d.

Note:
High temperature is one of the necessary conditions for nuclear fusion to take place. Apart from that high pressure is also necessary as it increases the frequency of collision of the light nuclei to enhance the rate of fusion. The temperature required for fusion is of the order $\text{1}{{\text{0}}^{\text{6}}}\text{K}$, which exists in the interior of the sun.