AQA GCSE Combined Science Physics Paper 1 Revision

• Units for quantities


  • Energy/Work - Joules
  • Speed - Meters per second
  • Mass - Kilograms
  • Height - Meters
  • Power - Watts
  • Time - Seconds
  • Charge - Coulombs
  • Potential Difference - Volts
  • Current - Amps
  • Resistance - Ohms
  • Density - Kilograms per meter cubed
• System


  An object or group of objects that can store energy
• Ways energy can be stored

  • Magnetic
  • Kinetic
  • Thermal
  • Gravitational potential
  • Chemical
  • Elastic potential
  • Electrostatic
  • Nuclear
• Conservation of energy


  In a closed system, energy can't be created or destroyed, only transferred between stores
• Calculating gravitational potential energy


  1. Write down the equation

  2. Substitute the values (mass, gravitational field strength, height)

  3. Calculate the answer and include the units (Joules)
• Calculating kinetic energy


  1. Write down the equation

  2. Substitute the values (mass, velocity)

  3. Calculate the answer and include the units (Joules)
• Calculating elastic potential energy

  1. Write down the equation

  2. Substitute the values (spring constant, extension)

  3. Calculate the answer and include the units (Joules)
• Specific heat capacity


  The maximum amount of energy a substance will absorb to change its temperature by 1 degree Celsius per kilogram
• Calculating change in energy using specific heat capacity

  1. Write down the equation (change in energy = mass x specific heat capacity x change in temperature)

  2. Substitute the values

  3. Calculate the answer and include the units (Joules)
• The required practical is to find the specific heat capacity of a metal block or liquid
• Change in temperature


  Difference between starting and ending temperature
• Mass


  Must be in kilograms (if given in grams, divide by 1000)
• Specific heat capacity


  How much energy it takes to heat up 1 kg by 1 degree C
• Required practical to find specific heat capacity


  1. Given metal block or container of liquid

  2. Use balance to measure mass

  3. Insulate to minimise energy losses

  4. Use thermometer to measure temperature change

  5. Use electrical heater to heat up

  6. Calculate energy transferred using voltmeter, ammeter and stopwatch
• Power


  Rate at which energy is transferred or work is done
• More powerful appliance


  Faster it can do work or transfer energy
• Calculating power


  Energy (in joules) divided by time (in seconds)
• Efficiency


  Proportion of energy that has been usefully transferred, can be expressed as decimal or percentage
• Conservation of energy - same amount of energy at end as start, but some transferred wastefully
• Ways to reduce wasted energy

  • Reduce heat loss by insulating
  • Reduce drag by streamlining
  • Reduce friction by using wheels or lubricating
• Renewable energy resources


  Being generated faster than used
• Non-renewable/finite energy resources


  Being used faster than generated
• Factors to consider for each energy resource

  • Renewable/non-renewable
  • Cost
  • CO2 emissions
  • Reliability
  • Geographic restrictions
  • Radioactive waste disposal and risks (for nuclear)
• Need to know all circuit symbols and be able to draw circuits properly
• Current


  Speed of flow of charge around circuit
• Potential difference


  Amount of energy being transferred by a component
• Required practical 15 - Measuring IV characteristics

  1. Use ammeter in series, voltmeter in parallel

  2. Calculate resistance using R=V/I

  3. Investigate how resistance changes with wire length and with resistors in series/parallel
• Required practical 16 - Investigating current and potential difference for circuit components

  1. Use ammeter in series, voltmeter in parallel

  2. Draw IV graphs for different components
• IV graphs


  • Ohmic conductor - linear, proportional
  • Filament lamp - S-shaped curve, resistance increases with temperature
  • Diode - only allows current flow in one direction, small potential difference before current starts flowing
• Light dependent resistor


  Resistance decreases as light gets brighter
• Thermistor


  Resistance decreases as temperature increases
• Series circuit


  Only one path for charges to follow
• Parallel circuit


  Charges split at junction, go through different paths
• In series circuit


  Current is the same everywhere
• In parallel circuit


  Currents in branches add up to total current
• In series circuit


  Potential difference split between components
• In parallel circuit


  Potential difference the same across each component
• Electrical circuit


  1. Current splits into branches

  2. Current in branches adds up to total current

  3. Potential difference splits between components in series

  4. Potential difference is full for each component in parallel

  5. Total resistance in series is sum of individual resistances

  6. Total resistance in parallel is less than smallest individual resistance
• Alternating current (AC)


  Current that repeatedly changes direction, 50 times per second in UK
• Direct current (DC)


  Current that only flows in one direction