Nuclear Fusion (OCR GCSE Physics A (Gateway)): Revision Note

Exam code: J249

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Nuclear Fusion

  • Small nuclei can react to release energy in a process called nuclear fusion

  • Nuclear fusion is defined as:

    When two light nuclei join to form a heavier nucleus

  • This process requires extremely high temperatures to maintain

    • This is why nuclear fusion has proven very hard to reproduce on Earth

  • Stars use nuclear fusion to produce energy

  • In most stars, hydrogen atoms are fused together to form helium and produce lots of energy

nuclear fusion, IGCSE & GCSE Physics revision notes

Two hydrogen nuclei are fusing to form a helium nuclei

  • The energy produced during nuclear fusion comes from a very small amount of the particle’s mass being converted into energy

  • Albert Einstein described the mass-energy equivalence with his famous equation:

E = m × c2

  • Where:

    • E = energy released from fusion in Joules (J)

    • m = mass converted into energy in kilograms (kg)

    • c = the speed of light in metres per second (m/s)

  • The amount of energy released during nuclear fusion is huge:

    • The energy from 1 kg of hydrogen that undergoes fusion is equivalent to the energy from burning about 10 million kilograms of coal

  • Designing a working fusion power station which produces more power than it uses is a major goal in engineering

    • ITER in France is currently the best performing fusion power station, almost giving out as much energy as it requires to power it

  • For fusion in a power station, deuterium and tritium, heavy isotopes of hydrogen are used

The fusion of deuterium and tritium to form helium with the release of energy

Worked Example

An example of a hydrogen fusion reaction which takes place in stars is shown here.

Fusion equation, downloadable IGCSE & GCSE Physics revision notes

Which of the following is a valid reason why hydrogen fusion is not currently possible on Earth?

A   Hydrogen fusion produces dangerous radioactive waste

B   Hydrogen nuclei require very high temperature to fuse together

C   Hydrogen is a rare element that would be difficult to get large amounts of

D   Hydrogen fusion does not produce enough energy to be commercially viable

Answer: B

  • Hydrogen nuclei have positive charges

  • So two hydrogen nuclei would have a repulsive force between them

  • High temperatures are required to give the nuclei enough energy to overcome the repulsive force

  • The answer is not A because the products of the hydrogen fusion shown in the reaction is helium

    • Helium is an inert gas

  • The answer is not C because hydrogen is a very abundant element

    • It is the most common element in the universe

  • The answer is not D because hydrogen fusion would produce a huge amount of energy

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Joanna

Author: Joanna

Expertise: Physics Content Creator

Joanna obtained her undergraduate degree in Natural Sciences from Cambridge University and completed her MSc in Education at Loughborough University. After a decade of teaching and leading the physics department in a high-performing academic school, Joanna now mentors new teachers and is currently studying part-time for her PhD at Leicester University. Her passions are helping students and learning about cool physics, so creating brilliant resources to help with exam preparation is her dream job!

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