CBSE 2025 · Region 7 · Set 1 · Q21 · 2 marks
Briefly explain how energy is produced in stars, giving two examples of the nuclear reactions involved.
Marking-scheme solution
Energy is produced in stars due to Nuclear fusion.
Two lighter nuclei fuse to form a heavier nucleus which is more stable, hence energy is released.
Alternatively: Due the difference in masses in reactants and products, mass is converted into energy. Hence energy is released.
NucleiMass-Energy and Nuclear Binding EnergyUnderstandvery_short_answermedium
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.