Nuclear Energy: o
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The energy released from the nuclear reactions, either fission or fusion, is called as nuclear energy.
Nuclear fusion and fission are manifestations of the equivalence of mass and energy.
In fusion light atom nuclei like Hydogen fuse to form a bigger nucleus whose mass is less than the sum of the masses of the reactants.
In fission, a heavy nucleus like uranium 235 U92, is split by a neutron into lighter nuclei. Once again the final mass is less than the initial mass and the mass difference translates into energy.
The Equivalence of Mass and Energy
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Physicists believed that in every physical and chemical process, the mass of an isolated system is conserved till Albert Einstein show the relation, E = m c 2 where c, the speed of light in vacuum is approximately 3 × 10 8 m s – 1. This equation showed that mass and energy are equivalent and are related by E = m c 2.
If there is a difference between the sum of reactants and products that differene, Dm, is called mass defect.
In case of chemical reactions the mass defect is very small and can be neglected, but in the case of nuclear reactions this becomes significant.
Principle of Conservation of Energy o
If the forces involved are non-conservative, part of the mechanical energy may get transformed into other forms such as heat, light and sound.
o However, the total energy of an isolated system does not change.
o Since the universe as a whole may be viewed as an isolated system, the total energy of the universe is constant.