Conservation, dissipation and national and global energy sources — WJEC GCSE Physics
In summary: Conservation, dissipation and national and global energy sources is a key topic in WJEC GCSE Physics. Key exam tip: Always state that energy is 'dissipated' rather than 'lost' when referring to energy becoming less useful.
Exam Tips for Conservation, dissipation and national and global energy sources
- Always state that energy is 'dissipated' rather than 'lost' when referring to energy becoming less useful.
- When discussing efficiency, ensure you can describe practical ways to increase it, such as using insulation or lubrication.
- Be prepared to compare different energy sources based on their environmental impact and sustainability.
- Use the provided efficiency formula carefully, ensuring units for energy are consistent.
Common Mistakes
- Confusing energy dissipation with energy loss (violating the conservation of energy principle).
- Failing to identify the role of free electrons in thermal conduction in metals.
- Incorrectly calculating efficiency by swapping input and output energy values.
- Misinterpreting the qualitative effects of wall thickness and thermal conductivity on cooling rates.
Marking Points
- Energy is dissipated in all system changes, becoming stored in less useful ways.
- The total energy of a closed system remains constant (no net change).
- Methods to reduce unwanted energy transfer include lubrication and thermal insulation.
- The rate of cooling of a building depends on the thickness and thermal conductivity of its walls.
- Heat transfer processes include conduction (role of free electrons in metals), convection, and radiation.
- Efficiency calculation: (output energy transfer / input energy transfer) * 100.
- Distinction between renewable and non-renewable energy sources.
- Identification of main energy sources: fossil fuels, nuclear, bio-fuel, wind, hydro-electricity, tides, and the Sun.
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