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⚛️ Physics  ·  Nuclei  ·  NEET & JEE

Nuclear fission vs fusion: which releases more energy per unit mass?

Answer: Fusion.

  • A Fission
  • B Fusion
  • C Equal
  • D Depends on temperature

Correct answer: B. Fusion

Explanation: Fusion releases more energy per unit mass. D-T fusion yields ~14.1 MeV per event with ~5 amu total, ~ 3 MeV/amu. Fission: U-235 yields ~200 MeV with 236 amu, ~ 0.85 MeV/amu.

Binding Energy per Nucleon vs Mass NumberMass number ABE/nucleonFe-56 (peak, most stable)FUSION region (light → medium)FISSION region (heavy → medium)Both processes release energy by moving nuclei toward the Fe-56 peak

Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.

Concept context

Radioactivity, nuclear reactions, fission, fusion, and binding energy.

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