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Subjects · Leaving Cert Physics & Chemistry

Leaving Cert Physics & Chemistry: Heating effect & electric power

How often Heating effect & electric power comes up on the Physics & Chemistry papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

OL Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Heating effect & electric power, Higher Level(9 marks)

Quick ones on Heating effect & electric power.

(a)The current through a fixed resistor is doubled for the same time. The heat produced is multiplied by…
  1. 2
  2. 4
  3. 8
(b)A 2 kW heater runs for 3 hours. Electricity costs 20 cent per kWh. Cost?
  1. €0.60
  2. €120.00
  3. €1.20
(c)A 2300 W kettle runs on 230 V mains. Current drawn?
  1. 10 A
  2. 2.3 A
  3. 0.1 A
Show the answers

(a) 4

(b) €1.20

(c) 10 A

Your turn: Higher Level questions on Heating effect & electric power.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q5
2024Q5
2023Q5
2022Q5
2021Q5
2019Q5
2018Q5
2017Q1(k), Q5
2016Q6(c)

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

More Heating effect & electric power questions

Heating effect & electric power, 2 marks

What is the purpose of a fuse in a plug?

  1. It earths the metal case of the appliance if there is a fault
  2. It stores charge to smooth out the current to the appliance
  3. It melts and breaks the circuit if the current is too big
Show the answer

It melts and breaks the circuit if the current is too big

A fuse is a thin wire in series on the live side. Excess current heats and melts it, preventing overheating and fire. Its rating should be just above the normal working current.

Ordinary Level

Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q1(m), Q6(b)
2024Q1(m)
2023Q1(n), Q1(o), Q5
2022Q5
2021Q1(m), Q1(p)
2019Q1(j), Q5
2018Q1(d), Q1(h)
2017Q1(h), Q1(i), Q5
2016Q1(k), Q5

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

More Heating effect & electric power questions

Heating effect & electric power, 2 marks

Joule's law: heat produced in a resistor per second is proportional to?

  1. The current
  2. The voltage of the mains
  3. The square of the current
Show the answer

The square of the current

Doubling the current gives four times the heat. In the experiment, use a fixed mass of water in an insulated cup with a lid to reduce heat loss.

Heating effect & electric power, 3 marks

Current drawn by a 1150 W toaster on a 230 V supply?

  1. 50 A
  2. 5 A
  3. 0.2 A
Show the answer

5 A

P = VI, so I = P ÷ V = 1150 ÷ 230 = 5 A. Check: 230 × 5 = 1150 W.

Heating effect & electric power, 2 marks

A kilowatt-hour is?

  1. The energy used by a 1 kW appliance in 1 hour
  2. The power of a 1 kW appliance at any moment
  3. The current used by a 1 kW appliance in 1 hour
Show the answer

The energy used by a 1 kW appliance in 1 hour

The kWh is the unit of energy on electricity bills. kWh = power in kW × time in hours. One kWh is also called one unit.

Other Physics & Chemistry topics

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