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Leaving Cert Physics: The electron

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

HL Asked on 5 of the last 10 Higher Level papers, most recently in 2026.

OL Asked on 7 of the last 10 Ordinary Level papers, most recently in 2026. 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.

The electron, Higher Level(7 marks)

Quick ones on The electron.

(a)What is thermionic emission?
  1. The emission of electrons when light shines on a metal
  2. The emission of electrons from the surface of a hot metal
  3. The emission of alpha particles from a nucleus
(b)Mass of an electron?
  1. 1.6 × 10⁻¹⁹ kg
  2. 1.67 × 10⁻²⁷ kg
  3. 9.1 × 10⁻³¹ kg
(c)What did Millikan's oil drop experiment measure?
  1. The charge on the electron
  2. The speed of light
  3. The mass of the electron
Show the answers

(a) The emission of electrons from the surface of a hot metal

(b) 9.1 × 10⁻³¹ kg

(c) The charge on the electron

Your turn: Higher Level questions on The electron.

Higher Level

Asked on 5 of the last 10 Higher Level papers, most recently in 2026.

Every paper, year by year

YearWhere it came up
2026Q11
2025Not asked
2024Q14(c)
2023Not asked
2022Q6(k)
2021Not asked
2019Q8
2018Not asked
2017Not asked
2016Q12(b)

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

More The electron questions

The electron, 2 marks

Which evidence showed that cathode rays are negatively charged particles?

  1. They travel in straight lines and cast sharp shadows of objects in the tube
  2. They make the glass glow green where they strike the end of the tube
  3. They are deflected towards a positive plate and by a magnetic field
Show the answer

They are deflected towards a positive plate and by a magnetic field

Deflection by both electric and magnetic fields showed the rays carry charge, and the direction showed it is negative. Thomson measured their charge-to-mass ratio.

The electron, 2 marks

An electron is accelerated from rest through a potential difference of 2000 V. What kinetic energy does it gain?

  1. 1.6 × 10⁻¹⁹ eV
  2. 2000 eV
  3. 2000 J
Show the answer

2000 eV

Energy = charge × pd. For one electron through 1 V the energy is 1 eV, so 2000 V gives 2000 eV = 2000 × 1.6 × 10⁻¹⁹ = 3.2 × 10⁻¹⁶ J.

Ordinary Level

Asked on 7 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q12
2025Not asked
2024Not asked
2023Q12
2022Q12
2021Q13
2019Q10
2018Q10
2017Not asked
2016Q10

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

More The electron questions

The electron, 3 marks

A beam of cathode rays passes between two charged metal plates. It bends towards?

  1. The negative plate
  2. Neither plate
  3. The positive plate
Show the answer

The positive plate

Cathode rays are negative electrons, so they are attracted to the positive plate. This is how the beam is steered in a cathode ray tube.

The electron, 2 marks

Where are electrons found in an atom?

  1. Inside the protons
  2. Orbiting the nucleus
  3. Inside the nucleus
Show the answer

Orbiting the nucleus

The nucleus holds the protons and neutrons. The negative electrons move around it.

The electron, 2 marks

What are cathode rays?

  1. Streams of electrons
  2. Streams of protons
  3. Streams of alpha particles
Show the answer

Streams of electrons

In a cathode ray tube, electrons are given off by a hot cathode (thermionic emission) and accelerated towards the anode.

Other Physics topics

All of Leaving Cert Physics