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CIE iGCSE Co-ordinated Sciences-P1.6.3 Energy resources- Study Notes- New Syllabus

CIE iGCSE Co-ordinated Sciences-P1.6.3 Energy resources – Study Notes

CIE iGCSE Co-ordinated Sciences-P1.6.3 Energy resources – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.

Key Concepts:

Core

  • Describe how useful energy may be obtained, or electrical power generated, from:
    (a) fossil fuels
    (b) biofuels
    (c) water, including waves, tides, and
    hydroelectric dams
    (d) geothermal resources
    (e) nuclear fission
    (f) light from the Sun (solar cells)
    (g) infrared and other electromagnetic waves from the Sun to heat water (solar thermal collectors)
    (h) wind (wind turbines) including references to a boiler, turbine and generator where they are used
  • Give advantages and disadvantages of each method in terms of renewability, availability, reliability, scale and environmental impact
  • Understand, qualitatively, the concept of efficiency of energy transfer
  • Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal

Supplement

  • Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal
  • Know that energy is released by nuclear fusion in the Sun (detailed knowledge of the process of fusion is not required)
  • Know that energy is released by nuclear fission in nuclear reactors (detailed knowledge of the process of fission is not required)
  • Define efficiency as:
    (a) efficiency = useful energy output / total energy input × 100%
    (b) efficiency = useful power output / total power input × 100% recall and use the equations

CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics

Methods of Generating Useful Energy / Electrical Power

Energy can be obtained or electrical power generated from a variety of sources. Each source has its own method of converting stored or natural energy into useful energy.

(a) Fossil Fuels (Coal, Oil, Natural Gas)

  • Fossil fuels store chemical energy.
  • Burning the fuel releases heat, which boils water in a boiler to produce steam.
  • The steam drives a turbine, which rotates a generator to produce electricity.
  • Waste energy is often released as heat to the surroundings.
  • Example: Coal-fired power plants, gas-fired power stations.

(b) Biofuels

  • Biofuels (wood, ethanol, biogas) store chemical energy from organic material.
  • They are burned to release heat, which can boil water in a boiler to produce steam.
  • The steam drives a turbine connected to a generator to produce electricity.
  • Biofuels are renewable if grown sustainably, but burning releases CO₂.

(c) Water – Waves, Tides, and Hydroelectric Dams

  • Hydroelectric dams: Water stored at height has gravitational potential energy.
  • Water released flows through turbines, causing them to rotate.
  • The turbine drives a generator to produce electricity.
  • Tidal power: Uses rising and falling tides to turn turbines.
  • Wave power: Buoys or floating devices convert wave motion to mechanical energy, which drives generators.

(d) Geothermal Resources

  • Geothermal energy comes from heat stored inside the Earth.
  • Hot water or steam is extracted from underground reservoirs.
  • Steam can directly drive a turbine connected to a generator.
  • Used in places with volcanic activity or hot rocks close to the surface.

(e) Nuclear Fission

  • Nuclear fission releases energy from splitting atoms (usually uranium-235 or plutonium-239).
  • Heat from fission is used to boil water in a boiler or reactor vessel.
  • The steam drives a turbine connected to a generator to produce electricity.
  • Produces radioactive waste that must be managed safely.

(f) Light from the Sun – Solar Cells (Photovoltaics)

  • Solar cells convert sunlight directly into electrical energy using the photovoltaic effect.
  • No moving parts are required.
  • Used for powering homes, calculators, satellites, and remote locations.

(g) Infrared and Other Electromagnetic Waves – Solar Thermal Collectors

  • Solar thermal collectors absorb infrared and other electromagnetic radiation from the Sun.
  • Heat is transferred to water or another fluid, storing energy as thermal energy.
  • Hot water can be used directly for heating or indirectly to produce steam that drives a turbine and generator.
  • Used in domestic water heating and solar power stations.

(h) Wind – Wind Turbines

  • Wind has kinetic energy due to moving air.
  • Blades of a wind turbine capture this kinetic energy, causing the rotor to spin.
  • The rotor drives a generator to produce electrical energy.
  • Renewable and produces no emissions during operation.

Example:

Why is nuclear fusion in the Sun considered the original source of nearly all energy on Earth?

▶️ Answer/Explanation

Because the Sun’s fusion reactions release light and heat, which drive photosynthesis, wind, the water cycle, and solar power. Fossil fuels, biofuels, wind energy, and hydroelectric power all trace their origin back to the Sun’s fusion energy.

Example:

A town uses three energy sources to supply electricity: a coal-fired power plant, a wind farm, and a solar farm.

  • The coal-fired plant burns 500 kg of coal, releasing \( 2 \times 10^7~\text{J} \) of chemical energy. Only 35% is converted to electrical energy.
  • The wind farm captures $\rm{1.5 \times 10^7}$ J of kinetic energy from wind; 80% is converted to electricity.
  • The solar farm receives $\rm{8 \times 10^6}$ J of sunlight; 15% is converted to electrical energy via solar cells.

Calculate the electrical energy supplied by each source and identify which source supplies the most electricity.

▶️ Answer/Explanation

Coal-fired plant:

Electrical energy = \( 2 \times 10^7 \times 0.35 = 7 \times 10^6~\text{J} \)

Wind farm:

Electrical energy = \( 1.5 \times 10^7 \times 0.8 = 1.2 \times 10^7~\text{J} \)

Solar farm:

Electrical energy = \( 8 \times 10^6 \times 0.15 = 1.2 \times 10^6~\text{J} \)

Conclusion: The wind farm supplies the most electricity (\( 1.2 \times 10^7~\text{J} \)), followed by the coal-fired plant (\( 7 \times 10^6~\text{J} \)) and the solar farm (\( 1.2 \times 10^6~\text{J} \)).

Key Point: Efficiency plays a crucial role in determining how much energy is actually supplied, even if the input energy is large.

Advantages and Disadvantages of Energy Sources

Different methods of generating energy have pros and cons based on key factors such as renewability, availability, reliability, scale, and environmental impact.

(a) Fossil Fuels (Coal, Oil, Natural Gas)

  • Advantages:
    • High energy density → large amount of energy per kg.
    • Reliable → can generate electricity continuously (base load power).
    • Available on large scale worldwide.
  • Disadvantages:
    • Non-renewable → will eventually run out.
    • Environmental impact → $\rm{CO_2}$ emissions, air pollution, acid rain.
    • Mining and extraction can damage ecosystems.

(b) Biofuels

  • Advantages:
    • Renewable if managed sustainably.
    • Can reduce waste (biogas from organic material).
    • Carbon neutral if crops regrow, absorbing $\rm{CO_2}$.
  • Disadvantages:
    • Availability depends on crops and climate.
    • Lower energy density than fossil fuels.
    • Large-scale production may compete with food supply.

(c) Water – Hydroelectric, Waves, Tides

  • Advantages:
    • Renewable → uses natural water cycle.
    • Reliable → especially dams with large reservoirs.
    • Can provide large-scale electricity.
  • Disadvantages:
    • Environmental impact → flooding of land, affecting ecosystems.
    • Dependent on rainfall → drought can reduce output.
    • High initial construction cost.

(d) Geothermal

  • Advantages:
    • Renewable and low emissions.
    • Reliable → continuous energy if reservoir is well managed.
    • Small land footprint.
  • Disadvantages:
    • Availability limited to regions with volcanic activity or hot rocks near surface.
    • High initial costs for drilling and infrastructure.
    • Risk of induced earthquakes.

(e) Nuclear Fission

  • Advantages:
    • Large-scale electricity generation with small fuel amounts.
    • Reliable → can run continuously (base load power).
    • Low greenhouse gas emissions during operation.
  • Disadvantages:
    • Non-renewable → limited uranium resources.
    • Radioactive waste → long-term storage issues.
    • High construction and decommissioning costs.
    • Accident risk (e.g., Chernobyl, Fukushima).

(f) Solar Cells (Photovoltaics)

  • Advantages:
    • Renewable → energy from sunlight.
    • Low running costs and minimal pollution.
    • Can be installed at small or large scales (rooftops or solar farms).
  • Disadvantages:
    • Intermittent → depends on sunlight and weather.
    • Energy storage (batteries) needed for continuous supply.
    • High initial installation cost.

(g) Solar Thermal Collectors

  • Advantages:
    • Renewable → direct use of Sun’s heat.
    • Can heat water or produce steam for turbines.
    • Low operating costs after installation.
  • Disadvantages:
    • Weather dependent → less efficient on cloudy days.
    • Large-scale solar thermal power requires significant land area.
    • High initial cost.

(h) Wind – Wind Turbines

  • Advantages:
    • Renewable → wind is a free and unlimited resource.
    • No greenhouse gas emissions during operation.
    • Can be installed onshore or offshore at various scales.
  • Disadvantages:
    • Intermittent → depends on wind speed.
    • Visual and noise impact.
    • Relatively small energy output per turbine compared to large power stations.

Example:

A town can generate electricity from either a coal-fired power plant or a wind farm.

  • The coal-fired plant releases \( 3 \times 10^7~\text{J} \) of chemical energy; 40% is converted to electricity.
  • The wind farm captures \( 2 \times 10^7~\text{J} \) of kinetic energy; 80% is converted to electricity.

Compare the electrical energy generated and discuss advantages and disadvantages in terms of renewability, availability, and environmental impact.

▶️ Answer/Explanation

Step 1: Calculate electrical energy from coal:

\( E_\text{coal} = 3 \times 10^7 \times 0.40 = 1.2 \times 10^7~\text{J} \)

Step 2: Calculate electrical energy from wind:

\( E_\text{wind} = 2 \times 10^7 \times 0.80 = 1.6 \times 10^7~\text{J} \)

Step 3: Compare advantages and disadvantages:

  • Coal-fired plant: Reliable and available at all times; high energy output; non-renewable; produces $\rm{CO_2}$ and pollutants; environmental damage from mining.
  • Wind farm: Renewable; low emissions; less energy output at times of low wind; intermittent → not always reliable; smaller environmental footprint.

Conclusion: The wind farm produces more electricity in this scenario due to higher efficiency, but its output can vary. Coal provides reliable base-load energy but has greater environmental impact and is non-renewable.

Efficiency of Energy Transfer (Qualitative)

Efficiency is a measure of how much of the input energy is converted into useful energy. It is always less than or equal to 100% because some energy is usually wasted, often as heat, sound, or vibrations.

Key Points:

  • Efficiency = how well energy is converted from one store to another.
  • Useful energy = energy that does the intended work (e.g., light from a bulb, motion from a motor).
  • Wasted energy = energy that is not useful and is often lost to the surroundings.
  • Energy is never destroyed, only transferred or dissipated (Law of Conservation of Energy).

Examples of Efficiency:

  • A torch battery supplies chemical energy. Most energy becomes light (useful), but some is wasted as heat → efficiency is less than 100%.
  • A car engine converts chemical energy in fuel to kinetic energy. Much energy is lost as heat and sound → low efficiency.
  • A wind turbine converts kinetic energy of wind to electrical energy. Some energy is lost to friction and sound → efficiency < 100%.

Example:

A 100 J battery is used in a torch. 70 J becomes light, and the rest is wasted as heat. Discuss efficiency qualitatively.

▶️ Answer/Explanation

Useful energy = 70 J (light)

Wasted energy = 30 J (heat)

Efficiency is less than 100% because not all energy is converted into useful light. Most energy is efficiently used, but some is lost as heat to surroundings.

Key Point: Efficiency explains why no machine or device can be perfectly 100% efficient.

Efficiency

Efficiency tells us how well a device or process converts input energy into useful output energy (or power). It is always expressed as a percentage.

Equations:

  • \( \text{Efficiency} = \dfrac{\text{Useful energy output}}{\text{Total energy input}} \times 100\% \)
  • \( \text{Efficiency} = \dfrac{\text{Useful power output}}{\text{Total power input}} \times 100\% \)

Key Notes:

  • Efficiency has no units because it is a ratio.
  • Efficiency is always less than or equal to \( 100\% \) (since some energy is always wasted, usually as heat or sound).
  • The higher the efficiency, the better the device is at converting input energy into useful output.

Example:

A light bulb receives \( 200~\text{J} \) of electrical energy per second. It produces \( 40~\text{J} \) of light energy per second, with the rest lost as heat.

▶️ Answer/Explanation

Using the equation: \( \text{Efficiency} = \dfrac{40}{200} \times 100\% = 20\% \).

Therefore, the light bulb is 20% efficient, with 80% of the input energy wasted as heat.

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