AQA whole of physics paper 1

• Energy is not something you can hold in your hand, it's just an idea
• Total energy in any interaction is always conserved, energy cannot be created or destroyed
• Energy can be turned into matter (Mass) but it's still technically true that energy cannot be created or destroyed
• Elastic potential energy

  Energy stored in a stretched or compressed spring, calculated as 1/2 * spring constant * extension^2
• Thermal energy

  Energy due to the random motion of particles, calculated as mass * specific heat capacity * temperature change
• Chemical potential energy

  Energy stored in chemical bonds, e.g. in food or fuels
• In a closed system, no energy is lost to the surroundings and no energy comes in from the surroundings
• If more energy is transferred to the surroundings than the system, it is not a closed system
• Measuring specific heat capacity

  1. Use an electric heater, voltmeter, ammeter, balance, timer and thermometer

  2. Calculate energy transferred = power * time

  3. Use rearranged specific heat capacity equation to find value
• Efficiency

  The ratio of useful energy output to total energy input, expressed as a decimal or percentage
• Electricity

  The flow of electric charge (electrons) that transfers energy from a source to a component
• Potential difference (PD) / Voltage

  The energy transferred per unit of charge, measured in volts
• Resistance

  The opposition to the flow of electric current, measured in ohms
• PD and current or V and I

  Directly proportional
• Steeper gradient of the line

  Lower the resistance of the resistor
• Graph for a bulb

  • Curved graph
  • Resistance is changing
  • Resistance of the metal filament increases with higher PD and current
• Higher current leads to more frequent collisions between electrons and ions, making it harder for electrons to flow, increasing resistance
• Resistors are specially made from specific materials so their resistance stays constant even if temperature changes
• Diode

  • Only lets current flow through in one direction
  • In one direction, resistance is very high, in the other, resistance is very low
• LED (light emitting diode)

  Similar to a diode, but emits light
• Measuring resistance of a metal wire

  1. Connect wire to circuit with crocodile clips

  2. Measure V and I

  3. Calculate R using Ohm's law

  4. Move one clip to see how length affects resistance
• Series circuit

  • Total PD is shared between components
  • Current is the same for all components
  • Total resistance is the sum of all resistances
• Potential divider circuit


  Series circuit where total PD is shared between components
• Parallel circuit

  • PD is the same for every branch
  • Current is shared between each branch
  • Total resistance decreases as more resistors are added
• Power

  • Rate of energy transfer
  • P = VI or P = I^2R
• Direct current (DC)


  Current that only flows in one direction
• Alternating current (AC)

  Current that alternates direction, resulting from an alternating PD
• National grid

  • Network of power stations, cables and transformers that transmit electricity across the country
• Step-down transformer


  Reduces voltage from high transmission levels to 230V for homes
• Electrostatic charge


  Caused by transfer of electrons when insulating materials are rubbed together
• Electric field


  Represents the force exerted on a positive charge, shown by field lines
• Measuring density of regular objects

  Measure dimensions to calculate volume, weigh to get mass, then use density = mass/volume
• Measuring density of irregular objects

  Use displacement method - lower object into water and measure volume of water displaced
• Ruler

  Not accurate for dimensions a few millimeters in length, resolution likely just 1 mm
• Vernier calipers


  More accurate for small dimensions, resolution of 0.1 mm
• Micrometer

  Accurate for very thin objects like wires, resolution of 0.01 mm
• Measuring volume of irregular object

  1. Use displacement can (Eureka can)

  2. Tie thin string around object

  3. Lower object until just under water line

  4. Wait for water to stop dripping into beaker

  5. Measure volume of water displaced
• States of matter


  • Solid
  • Liquid
  • Gas
• Gases have particles far apart and moving randomly, can be compressed
• At melting point (0°C), temperature remains constant until all ice has melted