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Leaving Cert Physics: Nuclear energy

How often Nuclear energy comes up on the Physics papers, every year it was asked, and questions to try.

HL Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 8 of the last 10 Ordinary Level papers, most recently in 2025. most years

June 2027 is the first exam on the new Physics course. These come from the 2016–2026 papers, so read them as a guide.

Nuclear energy, Higher Level(7 marks)

Quick ones on Nuclear energy.

(a)Einstein's equation linking mass and energy?
  1. E = mc
  2. E = mc²
  3. E = ½mc²
(b)Energy released when 1.0 × 10⁻⁶ kg of mass is converted into energy (c = 3.0 × 10⁸ m s⁻¹)?
  1. 3.0 × 10² J
  2. 9.0 × 10¹⁶ J
  3. 9.0 × 10¹⁰ J
(c)Where is an uncontrolled nuclear chain reaction used?
  1. In a nuclear bomb
  2. In a smoke detector
  3. In a nuclear power station
Show the answers

(a) E = mc²

(b) 9.0 × 10¹⁰ J

(c) In a nuclear bomb

Your turn: Higher Level questions on Nuclear energy.

Higher Level

Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q6(j)
2025Q6(k)
2024Q10
2023Q6(k), Q9
2022Q10
2021Q6(l), Q11
2019Q11
2018Q8
2017Q5(i)
2016Q9

Links open the State Examinations Commission’s paper for that year.

More Nuclear energy questions

Nuclear energy, 3 marks

Define nuclear fission.

  1. The joining together of two light nuclei into a heavier nucleus with the release of energy
  2. The emission of an alpha or beta particle from an unstable nucleus
  3. The splitting of a large nucleus into two smaller nuclei with the release of energy
Show the answer

The splitting of a large nucleus into two smaller nuclei with the release of energy

A slow neutron splits a uranium-235 nucleus, and the extra neutrons released can cause a chain reaction, which is controlled in a reactor.

Nuclear energy, 3 marks

Define nuclear fusion.

  1. The capture of an electron by a nucleus, turning a proton into a neutron
  2. The joining of two light nuclei to form a heavier nucleus with the release of energy
  3. The splitting of one heavy nucleus into two lighter nuclei with the release of energy
Show the answer

The joining of two light nuclei to form a heavier nucleus with the release of energy

Fusion of hydrogen into helium powers the Sun. It needs enormous temperatures to overcome the repulsion between the positive nuclei.

Nuclear energy, 2 marks

What is the mass defect of a nucleus?

  1. The difference between the mass of its separate nucleons and the mass of the nucleus
  2. The mass lost by the electrons of an atom during a chemical reaction
  3. The difference between the mass of the atom and the mass of all its electrons
Show the answer

The difference between the mass of its separate nucleons and the mass of the nucleus

A nucleus is lighter than its parts. The "missing" mass Δm is the binding energy divided by c², from E = mc².

Ordinary Level

Asked on 8 of the last 10 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q12
2024Q12
2023Q6(l), Q13
2022Q6(j)
2021Q12
2019Q12(d)
2018Not asked
2017Q10
2016Q12(d)

Links open the State Examinations Commission’s paper for that year.

More Nuclear energy questions

Nuclear energy, 2 marks

Which fuel is used in a nuclear fission reactor?

  1. Hydrogen
  2. Coal
  3. Uranium
Show the answer

Uranium

Uranium-235 nuclei split when struck by neutrons. Hydrogen is the fuel for fusion in the Sun; coal is burned in ordinary power stations.

Nuclear energy, 2 marks

Which equation links mass and energy?

  1. E = ½mv²
  2. E = mc²
  3. E = mgh
Show the answer

E = mc²

Einstein's E = mc²: a tiny mass is equal to a huge energy because c² = 9 × 10¹⁶ m² s⁻². mgh and ½mv² are potential and kinetic energy.

Nuclear energy, 2 marks

What is meant by the mass defect of a nucleus?

  1. The mass "missing" when protons and neutrons join to form the nucleus
  2. The mass of all the electrons that orbit around the nucleus
  3. The extra mass gained when protons and neutrons join together
Show the answer

The mass "missing" when protons and neutrons join to form the nucleus

A nucleus has less mass than its separate protons and neutrons. The missing mass has become binding energy (E = mc²).

Other Physics topics

All of Leaving Cert Physics