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| Nuclear Forces |
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The strong forces of attraction which firmly hold the nucleons in the nucleus are known as nuclear forces. |
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The forces holding the nucleus together must be extremely strong. This is clear from the fact that the positively charged protons remain confined to the small volume of the nucleus.
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If the nuclear forces are weak, the electrostatic repulsion of the positively charged protons would tend to break the nucleus apart or at the very least, the nucleus would occupy a much larger volume.
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Much is not known about the nuclear forces. However it is undoubtedly established that these forces exist between the nucleons i.e. between a neutron and a proton, between two protons and between two neutrons. The stability of the nucleus is accounted for due to the presence of these forces.
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Some important properties of nuclear forces are :
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They are attractive in character : |
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They exert attractive forces on the nucleons. Hence they are also called cohesive forces.
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They are charge independent : |
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They are the same between p and n or between p and p or between
n and n. These forces do not depend upon the charge on the
nucleons. |
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They are short range forces : |
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It has been found that they are quite strong for an internucleon
distance of the order of 10-15 m but become zero at an internucleon
distance of 10 -14 m. Nuclear forces change with distance
between the nucleons. |
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They have saturation character : |
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They abruptly become zero as the inter-nucleon distance is
increased to a certain value. Therefore, nuclear forces do
not increase with the increase in the number of nucleons.
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They are extremely strong : |
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Their magnitude is so high that a huge energy is required
to divide a nucleus into its constituents. The relative strengths
of gravitational (FG), electrostatic (Fe) and nuclear (FB) forces acting in the nucleus is given below,
FG : Fe : FB = 1 : 1036 : 1038 |
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The nuclear forces are dependent on the spin of the nuclei.
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Nuclear forces are non-central forces :
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The force between two nucleons does not act along the line joining their centers. This shows that nucleons in the nucleus is not spherically symmetric.
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