Overview
This lecture provides a fast-paced summary of all key topics for AQA GCSE Physics Paper 1, covering energy, electricity, particles, and atomic (nuclear) structure.
Energy Stores and Transfers
- Energy is a conserved quantity that cannot be created or destroyed, only transferred or converted.
- Main energy stores: kinetic, gravitational potential (GPE), elastic potential, thermal, and chemical.
- Kinetic energy: ( E = \frac{1}{2}mv^2 ).
- GPE: ( E = mgh ) (change in height only).
- Elastic potential: ( E = \frac{1}{2}ke^2 ).
- Thermal energy change: ( E = mc\Delta T ), with ( c ) as specific heat capacity (SHC).
- In closed systems, total energy before and after an event is equal.
- Efficiency: ( \text{Efficiency} = \frac{\text{useful energy out}}{\text{total energy in}} ); answer as decimal or %.
- Power: ( P = \frac{E}{t} ), measured in watts (W).
Electricity Basics
- Electricity is the flow of charge (electrons) in a closed circuit.
- Potential difference (PD or voltage): energy transferred per coulomb, measured in volts (V).
- Current (( I )): rate of flow of charge, ( I = \frac{Q}{t} ) (Q = charge in coulombs).
- Resistance (( R )): opposition to current, ( V = IR ) (Ohm’s law).
- Series circuits: PD shared, current same, resistances add.
- Parallel circuits: PD same, current shared, total resistance decreases.
- Special components:
- Diode allows current one way only.
- Thermistor: resistance decreases with heat.
- LDR: resistance decreases with light.
- Power in electrical circuits: ( P = VI ), ( P = I^2R ).
National Grid & Electrical Safety
- National Grid uses transformers to increase (step-up) and decrease (step-down) voltage for efficient transmission.
- Live (brown), neutral (blue), and earth (green/yellow) wires in plugs; earth and fuses for safety.
- AC (mains, 230 V, 50 Hz) vs. DC (batteries).
Particle Model of Matter
- Density: ( \rho = \frac{m}{V} ), measured in kg/m³.
- Solids, liquids, gases differ by particle arrangement and movement.
- Internal energy = kinetic energy + potential energy of particles.
- Heating increases kinetic energy; changing state increases potential energy (latent heat).
- Specific latent heat (( L )): ( E = mL ).
- Gas pressure increases with temperature or when volume decreases (at constant temperature, ( PV = \text{constant} )).
Atomic and Nuclear Physics
- Atom models evolved: plum pudding → nuclear model → shells → neutrons.
- Atomic (proton) number: number of protons; mass number: protons + neutrons.
- Isotopes: same element, different neutrons.
- Types of nuclear radiation:
- Alpha (( \alpha )): 2 protons, 2 neutrons, stopped by paper, strong ionizer.
- Beta (( \beta )): electron, stopped by aluminium, moderate ionizer.
- Gamma (( \gamma )): electromagnetic wave, weak ionizer, penetrates deeply.
- Half-life: time for half of radioactive nuclei/activity to decay.
- Nuclear fission: large nucleus split by neutron, releases energy and more neutrons (chain reaction).
- Nuclear fusion: two light nuclei combine, releasing energy (in stars).
Key Terms & Definitions
- Closed System — No energy in or out of the system.
- Specific Heat Capacity (SHC) — Energy needed to raise 1 kg of a substance by 1°C.
- Potential Difference (PD) — Energy per unit charge; measured in volts.
- Current — Rate of flow of charge.
- Resistance — Measure of how much a component opposes current.
- Isotope — Atom of the same element with different numbers of neutrons.
- Half-Life — Time for activity or nuclei count to halve.
- Latent Heat — Energy needed for a substance to change state without temperature change.
Action Items / Next Steps
- Practice calculations with all key energy, electricity, and radioactivity equations.
- Review required practicals (density, SHC, resistance).
- Ensure familiarity with circuit symbols, rules for series/parallel circuits, and transformer use.
- Learn definitions for key terms for short-answer questions.