Energy Resources and Efficiency

This guide covers the energy resources and efficiency parts of subtopic 1.7 Energy, work and power, from Topic 1, Motion, forces and energy, for Cambridge O Level Physics 5054, 2026–2028 series. The energy, work and power calculations that make up the rest of 1.7 are covered separately in Energy, Work and Power.

Where this fits in 5054

This is the applied, less formula-heavy half of subtopic 1.7 — how electricity generation actually draws on the energy stores introduced in Energy, Work and Power, and how efficiently a device or process converts the energy it’s supplied with into the useful output that was actually wanted.

Syllabus coverage

CAMBRIDGE O LEVEL PHYSICS 5054

• List renewable and non-renewable energy sources (1.7)
• Describe how useful energy may be obtained, or electrical power generated, from: chemical energy stored in fossil fuels; chemical energy stored in biofuels; hydroelectric resources; solar radiation; nuclear fuel; geothermal resources; wind; tides; and waves in the sea — including references to a boiler, turbine and generator where they are used (1.7)
• Describe advantages and disadvantages of each method, limited to whether it is renewable, when and whether it is available, and its impact on the environment (1.7)
• Define efficiency as (%) efficiency = useful energy output ÷ total energy input (× 100%), and as (%) efficiency = useful power output ÷ total power input (× 100%); recall and use these equations (1.7)

5054 is not tiered — every candidate covers all of the above.

Renewable and non-renewable energy resources

A non-renewable resource is used up faster than it can be replaced — the fossil fuels (coal, oil, natural gas) and nuclear fuel. A renewable resource is naturally replenished on a human timescale — biofuels, hydroelectric, solar, geothermal, wind, tidal and wave resources.

How each resource generates electrical power

Resource	How useful energy/power is obtained
Fossil fuels	Chemical energy released by burning heats water to steam in a boiler, which drives a turbine connected to a generator
Biofuels	Chemical energy from burning plant or waste material, used the same way as fossil fuels — a boiler produces steam to drive a turbine and generator
Hydroelectric	Falling or flowing water turns a turbine directly, connected to a generator
Solar	Radiation is converted to electricity directly (photovoltaic cells), or used to heat water
Nuclear	Nuclear fuel releases energy that heats water to steam via a boiler, driving a turbine and generator
Geothermal	Heat from the Earth heats water to steam, driving a turbine and generator
Wind	Moving air turns a turbine directly, connected to a generator
Tides	Moving water from rising and falling tides turns a turbine connected to a generator
Waves	The motion of waves on the sea surface drives a generator, often via a turbine-like mechanism

Notice the pattern: fossil fuels, biofuels, nuclear fuel and geothermal resources all work the same way — heat water to produce steam, and use the steam to spin a turbine connected to a generator — while hydroelectric, wind, tidal and wave power spin a turbine directly from moving water or air, without a heating stage. Solar is the exception that can skip the turbine and generator entirely, converting radiation to electricity directly.

Advantages and disadvantages

The syllabus deliberately limits this comparison to three factors: whether a resource is renewable, when and whether it is available (e.g. solar only works in daylight, wind depends on weather, tidal power is predictable but only at certain times), and its impact on the environment (e.g. fossil fuels release carbon dioxide and other pollutants on burning; nuclear fuel produces radioactive waste; hydroelectric dams and wind turbines change local landscapes and habitats, without combustion emissions).

Answering an “advantages and disadvantages” question well means staying within these three factors, rather than bringing in cost or reliability details the syllabus doesn’t ask for.

Efficiency

No real energy transfer converts all of its input into the useful output wanted — some is always transferred to stores that aren’t useful for the purpose at hand (commonly the internal/thermal store, as “wasted” heat). Efficiency measures what fraction of the input actually becomes useful output:

(%) efficiency = (useful energy output / total energy input) × 100%
(%) efficiency = (useful power output / total power input) × 100%

Worked example. A motor is supplied with 500 J of electrical energy and produces 350 J of useful kinetic energy. Find its efficiency.

efficiency = (350 / 500) × 100% = 70%

Worked example. A generator has a power input of 2000 W and a useful power output of 1600 W. Find its efficiency.

efficiency = (1600 / 2000) × 100% = 80%

Both formulas give the same answer for the same device, since power is just energy transferred per unit time — the ratio of useful-to-total is unchanged whether it’s measured as a total amount or as a rate.

Common mistakes

• Listing cost, reliability or public opinion as an “advantage” or “disadvantage.” The syllabus restricts this comparison to renewability, availability, and environmental impact only.
• Assuming every resource uses a turbine and generator. Solar power can generate electricity directly (photovoltaic), without either.
• Forgetting the ×100% in the efficiency equations, or reporting an efficiency above 100% (a sign of an arithmetic error, since useful output can never exceed total input).
• Confusing which resources are renewable. Nuclear fuel is non-renewable (it’s a finite fuel, mined like fossil fuels), even though it isn’t a fossil fuel — don’t group it with the renewables by mistake.

Quick revision checklist

• Renewable vs non-renewable, and which resources fall into each group
• How each of the nine named resources produces useful energy or electrical power, including where a boiler, turbine and/or generator is involved
• The three permitted comparison factors: renewable status, availability, environmental impact
• Both efficiency equations, and that they give the same answer for the same device

Related resources

• Energy, Work and Power — the rest of subtopic 1.7
• Cambridge O Level Physics subject hub

Written against Cambridge O Level Physics 5054, 2026–2028 series. Always check the current syllabus for your examination year.