Test: Nuclear Energy - JEE MCQ

James Chadwick set up an experiment to test his hypothesis. Chadwick put a piece of beryllium in a vacuum chamber with some polonium. The polonium emitted alpha rays, which struck the beryllium. When struck, the beryllium emitted the mysterious neutral rays.

A moderator is used in nuclear reactors in order to slow down the speed of neutrons.
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235 or a similar fissile nuclide.
Clearly, an obvious way to make a reactor work, and to make use of this characteristic of the 235U(n,f) cross-section, is to slow down the fast, fission neutrons. This can be accomplished, for example, when the neutrons collide with nuclei and scatter in some substance (a moderator).
 

Nucleus of hydrogen has only one proton. Hence its binding energy will be zero. The nuclear binding energy is the energy it takes to separate all the nucleons in a nucleus from each other. Since there is only the one nucleon, it's already separated from any other nucleons.

The fusion of hydrogen into helium is more likely to take place at high temperature and high pressure, like the sun.

Packing fraction: - It tells about the stability of a nucleus.
Packing fraction=isotonic mass=molecular mass (atomic mass)/atomic mass
p.f.=M-A/A

Fusion reactions takes place at temperature about 107K. It requires this high temperature so that nucleus are moving at very high speed, so that they have high kinetic energy and can overcome the repulsion between nuclei and come together.

The fission process represented by the equation, _92​U²³⁵+₀​n¹→_56​Ba¹⁴⁴+₃₆​Kr⁸⁹+3₀​n¹
Masses of reactants =234.39+1.01=235.4amu 
Masses of products =143.28+88.89+3(1.01) =235.2amu
Energy released = mass difference =235.4−235.2=0.2amu=0.2×931∼200MeV
 

The sum of the atomic no. and atomic mass no. on the reactant and product should be equal .
therefore 9+4 = a+1
a = 12

Nuclear forces are short range forces. This is the only correct answer. Others are wrong. They are the strongest forces in nature and do not obey inverse square law.

Nuclear fusion is the process by which two or more atomic nuclei join together, or “fuse,” to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy, which is released.