AQA GCSE Physics Paper 1 Overview

Energy

• Definition: Energy is a concept that describes interactions in a system; it is conserved and can neither be created nor destroyed, only transformed (mass-energy equivalence applies only in nuclear physics).
• Energy Stores:
  • Kinetic Energy: Calculated using the formula:
    E_k = \frac{1}{2} mv^2
  • Where:
    • E_k = kinetic energy (Joules)
    • m = mass (kg)
    • v = velocity (m/s)
  • Gravitational Potential Energy (GPE):
    E_{gpe} = mgh
  • Where:
    • E_{gpe} = gravitational potential energy (Joules)
    • m = mass (kg)
    • g = gravitational field strength (9.8 or 10 N/kg)
    • h = height (m)
  • Elastic Potential Energy:
    E_{epe} = \frac{1}{2} kx^2
  • Where:
    • E_{epe} = elastic potential energy (Joules)
    • k = spring constant (N/m)
    • x = extension (m)
  • Thermal Energy: Change in thermal energy calculated as:
    E = mc\Delta T
  • Where:
    • E = change in thermal energy (Joules)
    • m = mass (kg)
    • c = specific heat capacity (J/(kg°C))
    • \Delta T = change in temperature (°C)
• Energy Transfer: Energy must be transferred for interactions, observable in closed systems where total energy is conserved. Example: GPE equals Kinetic Energy at different points in a roller coaster.

Power & Efficiency

• Power: Rate of energy transfer, calculated using: P = \frac{E}{T}
  • Where:
  • P = power (Watts)
  • E = energy (Joules)
  • T = time (seconds)
• Efficiency: \text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}}
  • Efficiency can be expressed as a ratio or percentage. Example:
  • If a 200W laptop provides 120W useful energy:
  • Efficiency:
    \text{Efficiency} = \frac{120}{200} = 0.6 \text{ or } 60\%
• Energy Sources:
  • Non-renewable: Fossil fuels, nuclear fuels.
  • Renewable: Solar, wind, hydroelectric, geothermal, biofuels.

Electricity Basics

• Definition: Electric current is the flow of charge (usually electrons).
• Basic Circuit Components:
  • Battery: Stores chemical energy, converts to electrical energy in a circuit.
  • Complete Loop: Necessary for charge to flow, current flows from positive to negative terminal.
• Potential Difference (Voltage): V = \frac{E}{Q}
  • Where:
  • V = potential difference (Volts)
  • E = energy (Joules)
  • Q = charge (Coulombs)
• Current: I = \frac{Q}{T}
  • Where:
  • I = current (Amperes)
  • Q = charge (Coulombs)
  • T = time (seconds)
• Resistance: V = IR
  • Resistance can be measured by rearranging to find R:
    R = \frac{V}{I}
• Series Circuits:
  • Current is the same; voltage is shared; total resistance is the sum.
• Parallel Circuits:
  • Voltage is the same; current is shared; total resistance decreases with additional pathways.

Particles and States of Matter

• Particle Model:
  • Density ($\rho$) calculated as:
    \rho = \frac{m}{V}
  • Where:
  • $\rho$ = density (kg/m³)
  • m = mass (kg)
  • V = volume (m³)
• States of Matter: Solids, liquids, gases; density related to particle arrangement.
  • Phase Changes: Occur at constant temperature, involving changes in potential energy while kinetic energy changes during temperature changes.
  • e.g., Melting or boiling require heat energy despite constant temperature during the phase change.
    • SLH Equation: E = mL
• Compressing Gases: Results in a pressure increase, where pressure and volume are inversely proportional under constant temperature conditions.
  P1V1 = P2V2

Atomic Structure

• Models of the Atom:
  • Plum pudding model (JJ Thompson) to nucleus model (Ernest Rutherford) to Bohr model (electron shells).
  • Isotopes: Atoms of the same element differing in neutron counts.
• Radiation Types:
  • Alpha Decay: $ ext{Nucleus} \rightarrow \text{Daughter Nucleus} + \text{Alpha Particle (He)}$
  • Beta Decay: Convert neutron to proton emitting an electron: $ ext{Nucleus} \rightarrow \text{Daughter Nucleus} + \text{Beta Particle}$
• Ionizing Power: Alpha (high, low penetration), Beta (moderate), Gamma (low ionization, high penetration).
• Radioactivity: Count-rate (activity in BQ = counts per second), and half-lives, where half-life ($t_{1/2}$) is the time taken for half the radioactive nuclei to decay.
  • Example Calculation:
  • If starting counts = 96 BQ, dropping to 12 BQ, the number of half-lives is how many times to halve 96:
  • 1st: 48, 2nd: 24, 3rd: 12 (thus, $t_h = 12/3 = 4$ months).
• Fission and Fusion:
  • Fission: Splitting of nuclei, releasing energy in a chain reaction (e.g., nuclear reactors).
  • Fusion: Combination of light nuclei releasing energy (e.g., in stars).