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, kinetic energy being used to strike the match, and heat, light and sound energy coming out
• With fireworks


  We have chemical energy stored, kinetic energy as it moves up, light, heat and sound energy as it explodes, and gravitational potential energy and kinetic energy as it falls back down
• The Law of Conservation of Energy states 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
• Wasted energy is any energy that comes out of a situation that was not intended
• Wasted energy dissipates into the surroundings and can't be collected and used
• Efficiency is equal to useful energy out over total energy in, or useful power out over total power in
• Renewable energy sources


  • Sun
  • Wind
  • Water (including tidal, hydroelectric, wave)
  • Geothermal
• Non-renewable energy sources


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


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


  • Intermittent (e.g. no sun at night, variable wind)
  • Can be expensive to install
  • Can be disruptive to local environment
• Advantages of fossil fuels and nuclear power


  • Readily available
  • Cheap
  • Quick start-up time
• Disadvantages of fossil fuels and nuclear power


  • Finite resources
  • Heavily polluting
  • Nuclear waste storage issues
  • Risk of nuclear accidents
• 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 (non-linear, through origin)
  • Diode (one-way flow)
  • Thermistor (changes with temperature)
• In a series circuit, the current is the same wherever you look
• In a parallel circuit, the current gets split between the branches
• Total resistance in series


  Resistors added together
• Total resistance in parallel


  One over the sum of one over each resistance
• Mains electricity in the UK is 230 volts and 50 hertz
• Safety features of a plug


  • Fuse wire
  • Earth wire
  • Cable grip
  • Double encased cable
• Power


  Equals potential difference times current
• Power


  Equals current squared times resistance
• Energy


  Equals power times time
• Energy


  Equals charge times potential difference
• The National Grid transmits electricity from power stations to homes via step-up and step-down transformers
• Solid particles


  In a fixed position, vibrate slightly