Is energy production still a separate topic in the current IB Physics syllabus?

Energy Production was Topic 8 in the IB Physics syllabus assessed before the 2025 course change. In the current course, first assessed in 2025, it is not presented as a separate numbered topic. Relevant ideas are distributed across work, energy and power, thermal energy transfers, the greenhouse effect, induction and nuclear fission. This means older Topic 8 questions may still provide useful practice, but not every legacy syllabus statement is necessarily required. Follow the syllabus and teaching plan specified by your school when deciding which older questions to complete.

What energy-production equations should I know for IB Physics?

The central relationships are $P=E/t$ and $\eta=E{useful}/E{input}$, with the equivalent efficiency expression using powers. Hydroelectric questions may use $P=\rho Qgh$, while wind questions may use $P=\frac{1}{2}\rho Av^3$. Solar calculations commonly use $P=IA$ and then multiply by efficiency for electrical output. Nuclear energy calculations can require $E=\Delta mc^2$, depending on the context. You must also be able to rearrange these equations and maintain consistent SI units.

How do I answer a Sankey diagram question in IB Physics?

First identify the total input, the useful output and each dissipated energy flow. Apply conservation of energy so that all output branches add to the input. If values are represented by arrow widths, measure each width perpendicular to the direction of flow and use the stated or inferred scale. Calculate efficiency by dividing the useful output by the total input, not by the wasted output. When explaining the diagram, state that energy is transferred to less useful stores rather than being destroyed.

What is the difference between efficiency and capacity factor?

Efficiency measures the fraction of input energy or power converted into useful output. Capacity factor measures actual energy generated over a period relative to the energy that would be generated by continuous operation at rated power. A turbine may have a high efficiency when operating but a low capacity factor if its energy source is unavailable much of the time. Wind and solar capacity factors are affected by weather and daily or seasonal variation. The two quantities are both ratios, but they answer different physical questions and should not be used interchangeably.

How should I compare renewable and non-renewable energy sources in an exam?

Organize the comparison around common criteria such as reliability, emissions, waste, power density, land use and response to demand. Make paired statements so that both sources are discussed under the same criterion. Explain why each advantage or limitation occurs, using physics such as intermittency, combustion or energy storage. Avoid unsupported absolute claims, especially statements that a source has no environmental effect. If the question supplies numerical data or a location, use that evidence to reach a qualified conclusion.

What are the most common mistakes in IB energy-production calculations?

Students often confuse power with energy, particularly when mixing kilowatts and kilowatt-hours. Another frequent error is entering a percentage efficiency as 35 rather than 0.35 in a calculation. Wind questions cause mistakes because power depends on the cube of wind speed, while hydroelectric questions require vertical height rather than pipe length. Nuclear calculations can fail when mass is not converted into kilograms before using $E=\Delta mc^2$. A final check of units, scale and whether the answer is physically reasonable catches many of these errors.

IB Physics Energy Production Explained: Exam Guide

RevisionDojo Team

•7/30/2026•13 min read

This site uses cookie tracking technologies. Learn more in our Cookie Policy.

IB Physics Energy Production Explained: Exam Guide

RevisionDojo Team

•7/30/2026•13 min read

IB Physics energy production explained in exam terms means understanding how primary energy sources are converted into electrical energy, calculating power and efficiency, interpreting energy-flow data, and evaluating different generating systems. The most frequently tested ideas are energy-conversion chains, Sankey diagrams, renewable versus non-renewable sources, thermal power stations, nuclear fission, wind and hydroelectric power, and the distinction between power, energy and capacity factor.

There is an important syllabus clarification. Energy Production was Topic 8 in the pre-2025 IB Physics course, but it is not a separate numbered topic in the current course first assessed in 2025. Its underlying physics now appears across areas including A.3 Work, energy and power, B.1 Thermal energy transfers, B.2 Greenhouse effect, D.4 Induction at HL, and E.4 Fission. Legacy Topic 8 questions remain valuable when their content matches your current syllabus, but you should check uncertain material against the syllabus followed by your school.

The energy-conversion model examiners expect

Most electricity generation follows a sequence of energy transfers. A thermal power station, for example, uses:

chemical or nuclear energy → thermal energy → kinetic energy of steam → mechanical energy of a turbine → electrical energy

The turbine does not itself produce electricity. It turns a generator, where electromagnetic induction converts mechanical energy into electrical energy. Solar photovoltaic cells are an important exception because they convert radiant energy directly into electrical energy without a turbine.

Generating system	Primary energy store or source	Important intermediate transfer	Final conversion
Fossil-fuel station	Chemical energy of fuel	Heating water produces steam	Turbine drives generator
Nuclear station	Nuclear energy released by fission	Coolant transfers energy to steam system	Turbine drives generator
Hydroelectric station	Gravitational potential energy of water	Moving water rotates turbine	Generator produces electricity
Wind turbine	Kinetic energy of moving air	Blades and shaft rotate	Generator produces electricity
Solar photovoltaic	Solar radiation	No thermal or turbine stage required	PV cells produce electricity directly

In an explanation question, name both the energy stores and the transfer mechanism. Writing only “heat becomes electricity” is too vague because it omits the turbine and generator stages.

Power, energy and efficiency calculations

The basic relationship is

P=\frac{E}{t}

where power is measured in watts, energy in joules and time in seconds. One watt equals one joule per second. Electrical generation is also commonly stated in kilowatts or megawatts, while energy supplied over time may be measured in kilowatt-hours.

Remember that kW is a unit of power, whereas kWh is a unit of energy:

1\text{ kWh}=1000\text{ W}\times3600\text{ s}=3.6\times10^6\text{ J}

Efficiency is the fraction of the input energy or power transferred usefully:

\eta=\frac{E_{\text{useful}}}{E_{\text{input}}}=\frac{P_{\text{useful}}}{P_{\text{input}}}

Multiply by 100 only when an answer is required as a percentage. Efficiency has no unit and cannot exceed 1, or 100 percent.

Worked exam-style example

A power station receives thermal energy at a rate of 1.5 GW and generates 540 MW of electrical power.

\eta=\frac{540\times10^6}{1.5\times10^9}=0.36=36\%

The rejected power is

P_{\text{wasted}}=1.5\text{ GW}-0.540\text{ GW}=0.96\text{ GW}

A strong solution converts both values to compatible units, gives the efficiency as either 0.36 or 36 percent, and identifies the remaining power as energy transferred to the surroundings, principally through cooling systems and exhaust gases.

Sankey diagrams and conservation of energy

A Sankey diagram represents energy or power flows using arrows whose widths are proportional to the quantities transferred. The main horizontal arrow normally shows useful output, while branches show energy dissipated to the surroundings.

For any complete diagram:

E_{\text{input}}=E_{\text{useful}}+E_{\text{wasted}}

Examiners may ask you to calculate an unknown flow, determine efficiency from arrow widths, or complete a diagram to scale. Measure widths perpendicular to the direction of the arrows and use a consistent scale.

A common misconception is that “wasted energy” disappears. Energy is conserved, but it becomes less useful because it is dispersed, usually as thermal energy at a relatively low temperature. This distinction is central to both Sankey diagrams and power-station efficiency.

Physics of the main energy sources

Thermal and nuclear power stations

Fossil-fuel and nuclear stations differ in their primary energy source but share much of the same conversion process. Fossil fuels release energy through combustion, whereas a reactor releases energy through controlled nuclear fission.

In a thermal fission reactor, a fissile nucleus absorbs a neutron and splits into smaller nuclei, releasing energy and additional neutrons. The moderator slows neutrons to increase the probability of further fission, control rods absorb neutrons to regulate the chain reaction, and the coolant removes thermal energy from the reactor core. These roles should not be interchanged in exam answers.

For nuclear calculations, energy released from a mass defect may be found using

E=\Delta mc^2

where the mass defect must be expressed in kilograms if energy is required in joules. If atomic mass units and electronvolts are used, follow the conversions provided in the physics data booklet or question.

Hydroelectric power

Water stored at height has gravitational potential energy. If mass $m$ falls through vertical height $h$ , the available energy is

E=mgh

For water flowing at volume rate $Q$ , the ideal available power is

P=\rho Qgh

where $\rho$ is water density. Actual electrical output is lower, so a system efficiency may be included:

P_{\text{electrical}}=\eta\rho Qgh

Use the vertical height difference, not the length of a sloping pipe. Also check whether flow rate is given in cubic metres per second or requires conversion.

Wind power

For air of density $\rho$ moving at speed $v$ through swept area $A$ , the mass passing each second is $\rho Av$ . Combining this with kinetic energy per unit mass gives the available wind power:

P_{\text{wind}}=\frac{1}{2}\rho Av^3

The cubic dependence matters: doubling wind speed increases the available power by a factor of eight, assuming density and area remain constant. A real turbine extracts only a fraction of this power, so questions may supply an efficiency or power coefficient.

Do not write that all kinetic energy can be removed from the air. Air must continue moving behind the turbine, and mechanical and electrical losses further reduce output.

Solar power

If solar intensity $I$ falls normally on panel area $A$ , the incident power is

P_{\text{incident}}=IA

The electrical output is

P_{\text{output}}=\eta IA

Questions may add an angle, hours of usable sunlight, cloud cover or a capacity factor. Read carefully to determine whether the stated value is instantaneous power, average power or energy over a period.

Capacity factor is not efficiency

Efficiency compares useful output with energy input. Capacity factor compares actual energy generated with the maximum energy that could have been generated if a plant operated continuously at rated power:

\text{capacity factor}=\frac{E_{\text{actual}}}{P_{\text{rated}}t}

A wind farm can have efficient turbines but a modest capacity factor because wind is intermittent. A power station can also have a high conversion efficiency but a low capacity factor if it operates only during periods of peak demand.

For example, a 20 MW wind farm operating for 30 days has a maximum possible output of

20\text{ MW}\times(30\times24\text{ h})=14\,400\text{ MWh}

If it actually generates 5,040 MWh, its capacity factor is 0.35 or 35 percent. Capacity factor therefore concerns output over time, not the fraction of wind energy converted on a particular occasion.

Comparing energy sources in extended responses

Questions using compare, discuss or evaluate require more than a list of advantages. Make paired comparisons and explain the physical reason behind each point.

Criterion	Questions to consider
Reliability	Is output controllable, continuous or weather-dependent?
Power density	How much land or collector area is required?
Environmental effects	Are greenhouse gases, air pollutants, habitat changes or radioactive wastes produced?
Resource availability	Is the primary source renewable on a human timescale?
Response to demand	Can output be increased quickly? Is storage required?
Construction and operation	Are major dams, fuel transport, cooling systems or long construction periods involved?

Avoid absolute claims such as “solar power causes no pollution” or “nuclear power is completely clean.” Solar systems have manufacturing and land-use impacts, while nuclear generation creates radioactive waste and requires careful safety management. More precise statements, such as “no carbon dioxide is emitted during normal PV operation,” are easier to defend scientifically.

How energy-production questions appear in IB exams

The current IB Physics examination uses Paper 1A, Paper 1B and Paper 2, as shown in the official specimen papers for first examinations in 2025. Energy-production ideas can therefore appear in multiple-choice calculations, data-based interpretation, and short or extended responses rather than under one isolated topic heading.

Pay attention to command terms:

Calculate or determine: show substitution, working, units and an appropriate number of significant figures.
Explain: give a cause-and-effect chain using physics, not merely a description.
Outline: provide a brief account containing the essential stages.
Compare: refer to both systems throughout and identify similarities or differences.
Suggest: apply known physics to unfamiliar information supplied in the question.

Typical prompts ask students to determine efficiency from a Sankey diagram, calculate output from wind speed or water flow, explain losses in a thermal station, interpret generation data, or compare two sources for a stated location. When data are supplied, use them explicitly rather than replacing them with memorized generalizations.

An efficient revision method

Begin by learning the small set of equations and conversion chains, then practise identifying which quantity each question provides. Keep an error log for unit conversions, percentage efficiencies, powers of ten and command-term mistakes.

Use the IB Physics Questionbank for mixed practice, followed by the focused work, energy and power questions, thermal energy transfer questions, greenhouse effect questions, and fission questions. RevisionDojo’s IB Physics video library and per-question video solutions are particularly useful because they show how a complete method is converted into marks, including setup, substitution and explanation wording.

Conclusion

Energy production questions are built around a manageable set of principles: conservation of energy, power, efficiency, conversion chains, generators, source-specific equations and evidence-based comparison. The highest-value exam habit is to connect every calculation or explanation to a clearly defined physical system, while keeping power, energy, efficiency and capacity factor distinct.

RevisionDojo can support this process with syllabus-aligned IB Physics revision notes, the Questionbank and worked video solutions. After reviewing the theory, complete real questions and watch the corresponding solution method wherever available rather than relying on passive rereading.

Sources and referenced URLs

This site uses cookie tracking technologies. Learn more in our Cookie Policy.

IB Physics Energy Production Explained: Exam Guide | RevisionDojo

The energy-conversion model examiners expect

Most electricity generation follows a sequence of energy transfers. A thermal power station, for example, uses:

chemical or nuclear energy → thermal energy → kinetic energy of steam → mechanical energy of a turbine → electrical energy

Generating system	Primary energy store or source	Important intermediate transfer	Final conversion
Fossil-fuel station	Chemical energy of fuel	Heating water produces steam	Turbine drives generator
Nuclear station	Nuclear energy released by fission	Coolant transfers energy to steam system	Turbine drives generator
Hydroelectric station	Gravitational potential energy of water	Moving water rotates turbine	Generator produces electricity
Wind turbine	Kinetic energy of moving air	Blades and shaft rotate	Generator produces electricity
Solar photovoltaic	Solar radiation	No thermal or turbine stage required	PV cells produce electricity directly

In an explanation question, name both the energy stores and the transfer mechanism. Writing only “heat becomes electricity” is too vague because it omits the turbine and generator stages.

Power, energy and efficiency calculations

The basic relationship is

P=\frac{E}{t}

Remember that kW is a unit of power, whereas kWh is a unit of energy:

1\text{ kWh}=1000\text{ W}\times3600\text{ s}=3.6\times10^6\text{ J}

Efficiency is the fraction of the input energy or power transferred usefully:

\eta=\frac{E_{\text{useful}}}{E_{\text{input}}}=\frac{P_{\text{useful}}}{P_{\text{input}}}

Multiply by 100 only when an answer is required as a percentage. Efficiency has no unit and cannot exceed 1, or 100 percent.

Worked exam-style example

A power station receives thermal energy at a rate of 1.5 GW and generates 540 MW of electrical power.

\eta=\frac{540\times10^6}{1.5\times10^9}=0.36=36\%

The rejected power is

P_{\text{wasted}}=1.5\text{ GW}-0.540\text{ GW}=0.96\text{ GW}

Sankey diagrams and conservation of energy

For any complete diagram:

E_{\text{input}}=E_{\text{useful}}+E_{\text{wasted}}

Physics of the main energy sources

Thermal and nuclear power stations

For nuclear calculations, energy released from a mass defect may be found using

E=\Delta mc^2

Hydroelectric power

Water stored at height has gravitational potential energy. If mass $m$ falls through vertical height $h$ , the available energy is

E=mgh

For water flowing at volume rate $Q$ , the ideal available power is

P=\rho Qgh

where $\rho$ is water density. Actual electrical output is lower, so a system efficiency may be included:

P_{\text{electrical}}=\eta\rho Qgh

Use the vertical height difference, not the length of a sloping pipe. Also check whether flow rate is given in cubic metres per second or requires conversion.

Wind power

For air of density $\rho$ moving at speed $v$ through swept area $A$ , the mass passing each second is $\rho Av$ . Combining this with kinetic energy per unit mass gives the available wind power:

P_{\text{wind}}=\frac{1}{2}\rho Av^3

Do not write that all kinetic energy can be removed from the air. Air must continue moving behind the turbine, and mechanical and electrical losses further reduce output.

Solar power

If solar intensity $I$ falls normally on panel area $A$ , the incident power is

P_{\text{incident}}=IA

The electrical output is

P_{\text{output}}=\eta IA

Capacity factor is not efficiency

\text{capacity factor}=\frac{E_{\text{actual}}}{P_{\text{rated}}t}

For example, a 20 MW wind farm operating for 30 days has a maximum possible output of

20\text{ MW}\times(30\times24\text{ h})=14\,400\text{ MWh}

Comparing energy sources in extended responses

Questions using compare, discuss or evaluate require more than a list of advantages. Make paired comparisons and explain the physical reason behind each point.

Criterion	Questions to consider
Reliability	Is output controllable, continuous or weather-dependent?
Power density	How much land or collector area is required?
Environmental effects	Are greenhouse gases, air pollutants, habitat changes or radioactive wastes produced?
Resource availability	Is the primary source renewable on a human timescale?
Response to demand	Can output be increased quickly? Is storage required?
Construction and operation	Are major dams, fuel transport, cooling systems or long construction periods involved?

How energy-production questions appear in IB exams

Pay attention to command terms:

Calculate or determine: show substitution, working, units and an appropriate number of significant figures.
Explain: give a cause-and-effect chain using physics, not merely a description.
Outline: provide a brief account containing the essential stages.
Compare: refer to both systems throughout and identify similarities or differences.
Suggest: apply known physics to unfamiliar information supplied in the question.

An efficient revision method

Conclusion

Sources and referenced URLs

IB Physics Energy Production Questions: Exam Guide

Learn to solve IB Physics energy production questions using energy chains, efficiency, power, data analysis, and precise exam technique.

IB Physics Atomic & Nuclear Explained: Exam Guide

IB Physics atomic and nuclear explained for exams: spectra, decay, binding energy, fission, fusion, calculations, command terms, and revision tips.

The energy-conversion model examiners expect

Power, energy and efficiency calculations

Worked exam-style example

Sankey diagrams and conservation of energy

Physics of the main energy sources

Thermal and nuclear power stations

Hydroelectric power

Wind power

Solar power

Capacity factor is not efficiency

Comparing energy sources in extended responses

How energy-production questions appear in IB exams

An efficient revision method

Conclusion

Sources and referenced URLs

The energy-conversion model examiners expect

Power, energy and efficiency calculations

Worked exam-style example

Sankey diagrams and conservation of energy

Physics of the main energy sources

Thermal and nuclear power stations

Hydroelectric power

Wind power

Solar power

Capacity factor is not efficiency

Comparing energy sources in extended responses

How energy-production questions appear in IB exams

An efficient revision method

Conclusion

Sources and referenced URLs

IB Physics Energy Production Questions: Exam Guide

IB Physics Atomic & Nuclear Explained: Exam Guide

IB Physics Atomic & Nuclear Questions: Exam Guide

Continue studying with RevisionDojo

Frequently asked questions

Is energy production still a separate topic in the current IB Physics syllabus?

What energy-production equations should I know for IB Physics?

Features

Research

Platform

MYP Subjects

IB Subjects

IB Physics Energy Production Questions: Exam Guide

IB Physics Atomic & Nuclear Explained: Exam Guide

IB Physics Atomic & Nuclear Questions: Exam Guide

How do I answer a Sankey diagram question in IB Physics?

What is the difference between efficiency and capacity factor?

How should I compare renewable and non-renewable energy sources in an exam?

What are the most common mistakes in IB energy-production calculations?

IB Physics: How to Answer Fields (HL) Questions

IB Physics Energy Production: Mistakes and Fixes

IB Physics Fields (HL) Explained: Exam Guide