aqa physics paper 1

• Types of energy


  • Gravitational potential energy
  • Electrical energy
  • Elastic potential energy
  • Kinetic energy
  • Sound energy
  • Light energy
  • Nuclear energy
  • Chemical energy
  • Heat or thermal energy
• In a phone


  We have electrical energy going in, chemical energy being stored, and heat, light and sound energy coming out
• With a match


  We have chemical energy being stored and then kinetic energy being used to strike the match, and then heat, light and a bit of sound energy coming out
• With fireworks


  We have stored chemical energy that is transferred into kinetic energy as it moves up, and then light, heat and sound energy coming out, and then gravitational potential energy as it starts to fall, and kinetic energy as it falls back down
• The Law of Conservation of Energy tells us that energy cannot be created or destroyed, it is only transformed into another type of energy
• Kinetic energy


  Equal to half times mass times velocity squared
• Elastic potential energy


  Equal to half times the spring constant, times extension squared
• Gravitational potential energy


  Equal to mass times gravity times height
• Change in thermal energy

  Equal to mass times the specific heat capacity times change in temperature
• Power


  Equal to energy transferred over time
• Power


  Equal to work done over time
• While energy cannot be created or destroyed, it can be wasted
• Wasted energy is any energy that comes out of a situation that we didn't intend for it to be there
• Wasted energy dissipates into the surroundings, it spreads out so much it can't be collected and used
• Efficiency


  Equal to useful energy out over total energy in, can be expressed as percentage or decimal
• Efficiency


  Equal to useful power out over total power in, can be a percentage or a decimal
• Renewable energy sources


  • Sun
  • Wind
  • Water, including tidal power, hydroelectric power, wave power
  • Geothermal power
• Finite energy sources


  • Fossil fuels (coal, oil, gas)
  • Nuclear power
• Advantages of renewable energy sources

  • Don't release carbon dioxide
  • Inexhaustible
  • Generally non-polluting
• Disadvantages of renewable energy sources

  • Solar doesn't work at night or on cloudy/wintry days, can be expensive to install
  • Wind turbines can be disliked, don't work on non-windy days
  • Tidal and wave power can be disruptive to local environment
  • Hydroelectric dams involve flooding large areas
  • Geothermal power can only be used in volcanic countries
• Advantages of fossil fuels and nuclear power


  • Readily available, cheap, coal power stations have short start-up time
• Disadvantages of fossil fuels and nuclear power

  • Take millions of years to create, heavily polluting, potential risk of nuclear explosion, radioactive waste storage
• Circuit symbols


  • Cell
  • Battery
  • Ammeter
  • Voltmeter
  • Lamp/bulb
  • Diode
  • LED
  • Resistor
  • Variable resistor
  • Fuse
  • Thermistor
  • LDR
  • Closed switch
  • Open switch
• Charge


  Value of electricity flowing through circuits
• Current


  Flow of electrons
• Potential difference


  What pushes the current around
• Resistance


  Anything that slows down the current
• Charge


  Equals current times time
• Potential difference


  Equals current times resistance
• Current-potential difference graphs


  • Resistor at constant temperature (directly proportional)
  • Filament bulb (goes through zero)
  • Diode (only lets current flow in one direction)
  • Thermistor (changes with temperature)
  • LDR (changes with light intensity)
• In a series circuit, the current is the same wherever you look
• In a parallel circuit, the current gets split
• In a series circuit, you have to add up the different potential differences to get the total potential difference, and add up the different resistances to get the total resistance
• In a parallel circuit, the current on each branch is equal to the total current, but the potential difference on each branch is the same
• To find the total resistance in a parallel circuit, you need to do one over the resistance on each branch
• Mains electricity in the UK is 230 volts and 50 hertz
• Safety features of a plug

  • Fuse wire
  • Earth wire
  • Cable grip
  • Double encased plastic casing
• Power


  Equal to potential difference times current
• Power


  Equal to current squared times resistance
• Energy


  Equal to power times time