Overview
This lecture covers the key points of the GCSE Physics energy topic, including energy stores, transfers, calculations, efficiency, resources, and the National Grid.
Energy Stores
- There are eight energy stores: kinetic, thermal, gravitational potential, elastic potential, chemical, electrostatic, magnetic, and nuclear.
- Focus on understanding and explaining common energy stores and their examples.
Energy Transfers
- Energy transfers between stores through three main ways.
- Example: Dropping a ball converts gravitational potential energy to kinetic energy as it falls.
Key Equations
- Kinetic energy: ( E_k = \frac{1}{2}mv^2 ) (E = energy, m = mass, v = velocity).
- Gravitational potential energy: ( E_p = mgh ) (m = mass, g = gravitational field strength, h = height).
- Elastic potential energy involves the spring constant and extension; values are given in exams.
Specific Heat Capacity
- Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1°C.
- Equation: ( \Delta E = m \times c \times \Delta \theta ) (ΔE = change in energy, m = mass, c = specific heat capacity, Δθ = temperature change).
Conservation of Energy
- Energy cannot be created or destroyed, only transferred, stored, or dissipated.
- Total world energy remains constant; only the form changes.
Power
- Power is the rate of doing work: ( P = \frac{E}{t} ) (P = power, E = energy/work, t = time).
- "Work done" and "energy" are often interchangeable in calculations.
Heat Transfer: Conduction and Convection
- Conduction transfers heat through solids as vibrating particles pass energy.
- Convection transfers heat in liquids and gases, with hotter, less dense areas rising.
Efficiency and Reducing Unwanted Transfers
- Efficiency = useful output energy / total input energy.
- Methods for reducing heat loss at home include insulation, draft excluders, and double-glazing.
- No system is 100% efficient; some energy is always dissipated.
Energy Resources
- Renewable resources: solar, wind, hydroelectric, biofuel, tidal, geothermal; they are sustainable but can be unreliable.
- Non-renewable resources: fossil fuels and nuclear; reliable but cause environmental damage and will run out.
The National Grid
- The National Grid distributes electricity using step-up transformers (increase voltage) and step-down transformers (decrease voltage).
- Higher voltage reduces energy loss during transmission; final voltage is lowered for safe household use.
Key Terms & Definitions
- Kinetic Energy — energy of moving objects.
- Gravitational Potential Energy — energy due to an object’s position in a gravitational field.
- Elastic Potential Energy — energy stored in stretched or compressed objects.
- Specific Heat Capacity — energy needed to change temperature of 1 kg by 1°C.
- Conduction — heat transfer through solids.
- Convection — heat transfer in fluids (liquids and gases).
- Efficiency — ratio of useful output to total input energy.
- Renewable Resource — energy source that is naturally replenished.
- Non-renewable Resource — energy source that will eventually run out.
- The National Grid — network that distributes electricity across a country.
Action Items / Next Steps
- Memorize the eight energy stores and key equations.
- Understand and practice explaining energy transfer examples.
- Review pros and cons of different energy resources.
- Prepare for the next topic: Electricity.