Nuclei

Nuclear Force and Nuclear Energy


  • NUCLEAR FORCES are very strong attractive forces. They are charge independent and spin dependent.
  • Nuclear forces are short ranged i.e., they are applicable only when the separation of nucleon is of the order of 10−15 m.
  • The nuclear forces does not act along the line joining the centres of the nucleons.
  • Nuclear force is due to the exchange of π meson between nucleons.

  • The conversion of one element into another by artificial means is called ARTIFICIAL TRANSMUTATION of the element

  • The phenomenon of splitting up of a heavy nucleus into lighter fragments emitting large energy is called NUCLEAR FISSION.
  • Nuclear fission reaction by a thermal neutron is 92U235 + 0n1  →  56Ba141 + 36Kr92 + 3 0n1 + Q
  • The average number of neutrons released per fission in U235 is 2.5
  • Fission of Uranium and thorium is also possible with the high speed protons of energy 6.9 MeV or with deuterons of energy > 8 MeV
  • CHAIN REACTION is characterized by neutron multiplication factor "K"
    \tt K = \frac{Number \ of \ neutrons \ in \ present \ generation}{Number \ of \ neutrons \ in \ previous \ generation}
  • NEUTRON MULTIPLICATION FACTOR, K : If K < 1, then the reaction is said to be under critical.
  • If K = 1, then the reaction is said to be critical and energy will be produced at a steady rate.
  • If K > 1, then the reaction is said to be super critical (explosive)
  • The combination of two or more lighter nuclei forming comparatively heavier nucleus is called NUCLEAR FUSION.
  • Nuclear fusion takes place at a very high temperature (approx. 106 K)
  • Carbon – Nitrogen cycle 4 1H1 → 2He4 + 2 +1e0 + energy (26.7 MeV)
  • Proton – Proton Cycle 4 1H1 → 2He4 + 2 +1e0 + energy (26.7 MeV)
  • When a γ-ray photon of energy 1.02 MeV interacts with matter +1e0, -1e0 pair will be produced. This is referred as pair production.
    γ → +1e0, -1e0
  • If Eγ < 1.02 MeV then
    1) Pair production is not possible.
  • Electron emission is possible by photo electric emission.
  • If Eγ > 1.02 MeV then
    1) Pair - production is possible.
  • The extra energy will be shared equally by the pair of particles in the form of K.E.
  • BREEDER REACTOR : It converts non fissionable materials into fissionable material and generates electric power.
    \tt _{92}U^{238} + {_{0}N^{1}} \rightarrow {_{92}U^{239}} \ {\underrightarrow{2 \beta}} \ {_{94}U^{239}}
  • POWER REACTOR: Generates electric power P = nE/t
  • \tt P = \left(\frac{x}{A}N\right) \frac{E}{t} x = nuclear fuel in grams, N = Avogadro number, A = mass number, E = energy released per fission.
  • Breeder reactors are used to generate nuclear fuel.
Name Quarks Anti quarks
Symbol Charge Symbol Charge
Up U \tt + \frac{2}{3} e \tt \overline{u} \tt - \frac{2}{3} e
Down d \tt - \frac{1}{3} e \tt \overline{d} \tt + \frac{1}{3} e
Strange S \tt - \frac{1}{3} e \tt \overline{S} \tt + \frac{1}{3} e
Charmed C \tt + \frac{2}{3} e \tt \overline{C} \tt - \frac{2}{3} e
Top t \tt + \frac{2}{3} e \tt \overline{t} \tt - \frac{2}{3} e
Bottom b \tt - \frac{1}{3} e \tt \overline{b} \tt + \frac{1}{3} e

 

Nuclear Force View the Topic in this video From 00;18 To 13;29

View the Topic in this video From 00:26 To 5:03

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The chain reaction once started will either remains steady, accelerate or retard depending upon a factor called neutron reproduction or critical factor (k). If is defined as
\tt k = \frac{Rate \ of \ production \ of \ neutrons}{Rate \ of \ loss \ of \ neutrons}