Energy Resources and Electricity Generation
Where our energy comes from, how each source becomes electricity, and the trade-offs between them. Questions here are usually about evaluation — advantages and disadvantages — so learn them in pairs.
1. Renewable and non-renewable
Renewable — will not run out; replenished naturally. Non-renewable — finite; once used, gone on any human timescale.
| Renewable | Non-renewable |
|---|---|
| Solar | Coal |
| Wind | Oil |
| Hydroelectric | Natural gas |
| Tidal | Nuclear (uranium) |
| Wave | |
| Geothermal | |
| Biofuel |
Nuclear is NON-renewable, because uranium is a finite resource — even though it releases no CO₂ during generation. This catches people out because it is often grouped with “clean” energy.
Fossil fuels are coal, oil and natural gas — formed from the remains of organisms over millions of years.
2. How electricity is generated
Most methods share the same core process:
Something turns a TURBINE, which turns a GENERATOR, which produces electricity.
| Source | How the turbine is turned |
|---|---|
| Fossil fuels | burning heats water → steam drives the turbine |
| Nuclear | fission heats water → steam drives the turbine |
| Wind | the wind turns the blades directly |
| Hydroelectric | falling water turns the turbine |
| Tidal / wave | moving water turns the turbine |
| Geothermal | hot rocks heat water → steam drives the turbine |
| Solar cells | no turbine — light is converted directly to electricity |
Solar cells (photovoltaic) are the exception — they convert light directly into electricity, with no turbine and no generator. Solar panels (solar thermal) are different: they use the Sun’s energy to heat water.
The energy transfer chain for a fossil fuel station:
chemical → thermal → kinetic → electrical
For nuclear: nuclear → thermal → kinetic → electrical
3. Which resources come from the Sun?
Most of our energy traces back to the Sun:
From the Sun: solar, wind (uneven heating drives air movement), wave (driven by wind), hydroelectric (the Sun drives the water cycle), biofuel (photosynthesis), and fossil fuels (ancient photosynthesis).
NOT from the Sun: geothermal (radioactive decay in the Earth’s core), nuclear (energy stored in uranium nuclei), and tidal (the Moon’s gravitational pull, mostly).
Geothermal energy does NOT come from the Sun. This was a specific recorded error. Its energy comes from radioactive decay deep inside the Earth, which is why it works at night and in winter.
Tidal energy comes mainly from the Moon, not the Sun — the tides are caused by the Moon’s gravitational pull on the oceans.
4. Advantages and disadvantages
| Resource | Advantages | Disadvantages |
|---|---|---|
| Fossil fuels | reliable, high output, cheap infrastructure, available on demand | CO₂ → climate change; SO₂ → acid rain; finite |
| Nuclear | no CO₂, very high output from little fuel, reliable | radioactive waste, high build and decommissioning cost, accident risk |
| Solar | free, no pollution in use, good for remote areas | unreliable (no output at night, weather-dependent), high installation cost, large area needed |
| Wind | free, no pollution in use | unreliable, noise and visual impact, large area |
| Hydroelectric | reliable, no fuel cost, can respond quickly to demand | habitat flooding, displaces people, needs specific geography |
| Tidal | very predictable, no fuel cost | limited suitable sites, damages estuary habitats, high build cost |
| Geothermal | reliable, works day and night, no fuel | only viable in volcanically active regions |
| Biofuel | renewable, roughly carbon-neutral | uses land needed for food, still releases CO₂ when burnt |
The evaluation points that come up most:
Reliability — can it supply energy on demand? Fossil, nuclear, hydroelectric, geothermal and tidal are reliable; solar and wind are not. Environmental impact — CO₂, acid rain, habitat loss, visual and noise pollution. Cost — separate the initial installation cost from the running cost. Most renewables are expensive to build but cheap to run.
Frame cost answers properly. A recorded error mentioned “cost” vaguely; the mark comes from being specific — installation and maintenance costs are high, but there is no fuel cost.
5. Calculations
Power output: total energy ÷ time, or (power per unit) × (number of units).
Example. Each solar cell supplies 15 W. How many are needed for 100 W?
- 100 ÷ 15 = 6.67
- You need 7 cells — you cannot install two-thirds of a cell
Round UP when counting physical objects. A recorded error gave 6 instead of 7; six cells would supply only 90 W, which is not enough.
Efficiency: (useful output ÷ total input) × 100%.
6. Mistakes that cost marks
Calling nuclear renewable.
Saying geothermal energy comes from the Sun.
Saying tidal energy comes from the Sun.
Saying solar cells use a turbine.
Confusing solar cells with solar panels.
Giving vague cost answers instead of installation vs running costs.
Giving an advantage without a matching disadvantage when asked to evaluate.
Rounding down the number of units needed.
Saying renewables cause no pollution at all — manufacturing and construction do.
Frequently asked questions
What is a renewable resource? One that will not run out — it is replenished naturally.
Is nuclear renewable? No — uranium is finite.
How is electricity usually generated? Something turns a turbine, which turns a generator.
Which method doesn’t use a turbine? Solar cells — they convert light directly into electricity.
Which resources do not come from the Sun? Geothermal, nuclear and tidal.
Where does geothermal energy come from? Radioactive decay inside the Earth.
What causes the tides? Mainly the Moon’s gravitational pull.
What are the disadvantages of fossil fuels? CO₂ causing climate change, SO₂ causing acid rain, and they are finite.
Why is solar unreliable? No output at night, and it depends on the weather.
What’s the main drawback of nuclear power? Radioactive waste and high decommissioning costs.
Quick revision checklist
- I can classify every resource as renewable or non-renewable
- I know nuclear is non-renewable
- I know the general turbine → generator process
- I know solar cells are the exception
- I can distinguish solar cells from solar panels
- I know which resources originate from the Sun
- I know geothermal, nuclear and tidal do not
- I can give advantages and disadvantages for each resource
- I can discuss reliability, environmental impact and cost separately
- I distinguish installation cost from running cost
- I can write the energy transfer chain for a power station
- I round up when counting units
These notes cover energy resources and electricity generation in the Cambridge IGCSE Physics (0625) syllabus and are written for Grade 9–11 / Year 10–11 students. They are based on teaching patterns observed across a large set of one-to-one IGCSE Physics lessons, with particular attention to the errors students make most often and the wording examiners reward. Always check the current syllabus for your own exam series.
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