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Leaving Cert Physics: Domestic electricity

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

HL Asked on 4 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 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.

Domestic electricity, Higher Level(8 marks)

Quick ones on Domestic electricity.

(a)Colour of the earth wire in a modern appliance flex?
  1. Brown and blue
  2. Green and yellow
  3. Red and black
(b)Energy used by a 2.0 kW heater in 3.0 hours, in kilowatt hours?
  1. 6000 kWh
  2. 0.67 kWh
  3. 6.0 kWh
(c)What does an RCD (residual current device) do?
  1. It switches off the supply quickly if current leaks to earth
  2. It limits the voltage reaching the appliance
  3. It converts alternating current to direct current
Show the answers

(a) Green and yellow

(b) 6.0 kWh

(c) It switches off the supply quickly if current leaks to earth

Your turn: Higher Level questions on Domestic electricity.

Higher Level

Asked on 4 of the last 10 Higher Level papers, most recently in 2026.

Every paper, year by year

YearWhere it came up
2026Q13
2025Not asked
2024Not asked
2023Not asked
2022Q6(b)
2021Q6(i)
2019Not asked
2018Not asked
2017Q5(h)
2016Not asked

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

More Domestic electricity questions

Domestic electricity, 2 marks

What is the purpose of a fuse?

  1. It lowers the voltage supplied to the appliance so it runs cooler
  2. It connects the metal case to earth if a fault develops
  3. It melts and breaks the circuit if the current becomes too large
Show the answer

It melts and breaks the circuit if the current becomes too large

A thin wire that heats and melts above its rated current, protecting the flex and the appliance. It is always fitted in the live wire.

Domestic electricity, 2 marks

What advantage does an MCB have over a fuse?

  1. It detects small leaks of current to earth
  2. It can be reset instead of replaced
  3. It lets a larger current flow safely
Show the answer

It can be reset instead of replaced

An MCB (miniature circuit breaker) trips when the current is too high and is reset with a switch. Detecting leaks to earth is the job of an RCD.

Domestic electricity, 2 marks

What colour is the insulation on the live wire in a modern flex?

  1. Brown
  2. Blue
  3. Green and yellow
Show the answer

Brown

Live is brown, neutral is blue and earth is green and yellow. The fuse and the switch always go in the live wire.

Ordinary Level

Asked on 7 of the last 10 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q13
2024Q11
2023Not asked
2022Q6(k)
2021Q9
2019Q9
2018Not asked
2017Q11
2016Q12(c)

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

More Domestic electricity questions

Domestic electricity, 3 marks

Cost of running a 3 kW heater for 2 hours at 20 cent per kWh?

  1. €0.60
  2. €12.00
  3. €1.20
Show the answer

€1.20

Energy = 3 kW × 2 h = 6 kWh. Cost = 6 × 20 c = 120 c = €1.20. €0.60 forgets to multiply by the 2 hours.

Domestic electricity, 2 marks

Colour of the live wire in a modern plug?

  1. Green and yellow
  2. Brown
  3. Blue
Show the answer

Brown

Live is brown, neutral is blue and earth is green and yellow. The fuse is always in the live wire.

Domestic electricity, 2 marks

What does a miniature circuit breaker (MCB) do?

  1. Switches off automatically when the current is too large
  2. Measures the electrical energy used in kilowatt hours
  3. Steps down the mains voltage for small appliances
Show the answer

Switches off automatically when the current is too large

An MCB does the same job as a fuse, but it can be reset by flicking a switch instead of being replaced.

Other Physics topics

All of Leaving Cert Physics