Topic Papers Generate Energy resources and energy transfers units questions

Edexcel IGCSE Physics revision

Energy resources and energy transfers units questions

Distinguish joules from watts, choose consistent units, and show each conversion when calculating energy transfers.

Edexcel IGCSE Physics Subtopic 4.a

Energy resources and energy transfers units syllabus

Questions on energy resources and energy transfers units can test recall, calculations, explanations, diagrams, data handling and practical skills. You should be able to:

  • 4.1 use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second² (m/s²), newton (N), second (s) and watt (W)

How to answer energy resources and energy transfers units questions

  1. Write the unit symbol exactly and distinguish quantities that use similar-looking units.
  2. Convert prefixes and compound units before substituting values into an equation.
  3. Check that the unit of the final answer matches the quantity asked for.
  4. Use the context of a diagram or calculation to reject units with the wrong dimensions.

Energy resources and energy transfers units example questions and worked answers

These examples show how information in a diagram, graph or experimental context becomes part of a complete exam answer.

Example 1: Recognising an energy unit

June 2014 (R) · Paper 2P · Question 1(a)

Question 1

Which of these is a unit for energy?

A joule
B kilogram
C newton
D watt

Final answer

A — joule (J)

Mark scheme points

  1. M1 Select A: joule.

Explanation

The joule (J) is the unit of energy. A kilogram measures mass, a newton measures force, and a watt measures power.

Common mistakes

  • Do not choose watt: it is the unit of power, not energy.

Example 2: Reading the voltage for maximum motor efficiency

November 2020 (R) · Paper 1P · Question 8(d)(iv)

Question 2

A student uses this apparatus to investigate how the efficiency of an electric motor varies with its input voltage.

Apparatus diagram showing a d.c. power supply connected to a joulemeter and electric motor, with a 1.0kg mass suspended by string and a metre rule beside it.

This is the student’s method.

  • connect the electric motor to a d.c. power supply and a joulemeter
  • attach a 1.0kg mass to the electric motor using a length of string
  • set the voltage of the power supply to 10V and switch on the power supply
  • switch off the power supply when the mass has been lifted through a distance of 50cm
  • record the input energy to the motor from the joulemeter
  • calculate the energy transferred to the gravitational store of the mass
  • calculate the efficiency of the motor

The student repeats this process, setting the power supply to a different voltage each time.

The table shows the student’s results.

Power supply voltage
in V		 Joulemeter reading
in J		 Motor efficiency (%)
3.0 99.4 5.0
3.5 25.5 19.6
4.0 16.5 30.3
5.0 13.5 37.0
6.0 12.6 39.7
8.0 12.8 39.1
10.0 12.7
010203040500246810Power supply voltage / VMotor efficiency / %
An illustrative efficiency curve based on the experimental results.

Using the graph, determine the minimum power supply voltage that will allow the electric motor to operate at maximum efficiency.

power supply voltage = ________ V

Final answer

Power supply voltage ≈ 6.0 V.

Mark scheme points

  1. M1 Read the minimum voltage at which the graph reaches its maximum-efficiency region. Accept 5.4–6.6 V.

Explanation

The graph levels off at its maximum efficiency at about 6 V. The minimum voltage that gives this efficiency is therefore approximately 6.0 V.

Common mistakes

  • The examiner report describes the curve as rising smoothly before becoming flat above about 6 V. Read the start of this maximum-efficiency plateau, not a later voltage along it.

Practise Energy resources and energy transfers units questions

Build a focused practice set from this part of the Edexcel IGCSE Physics syllabus.

Generate Energy resources and energy transfers units questions View the Energy resources and energy transfers topic guide