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 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 cannot be collected and used
• Efficiency


  Equal to useful energy out over total energy in
• Efficiency


  Equal to useful power out over total power in
• Renewable energy sources


  • Sun
  • Wind
  • Water (including tidal, hydroelectric, wave)
  • Geothermal
• Finite 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, no wind on calm days)
  • Can be expensive to install
• 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 explosions
• 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


  Equal to current times time
• Potential difference


  Equal to current times resistance
• Current-potential difference graphs


  • Resistor at constant temperature (directly proportional)
  • Filament bulb (through zero)
  • Diode (one-way flow)
  • Thermistor (temperature dependent)
  • LDR (light dependent)
• 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


  Add the individual resistances
• Total resistance in parallel


  One over the sum of one over each individual 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 plastic casing
• Power


  Equal to potential difference times current
• Power


  Equal to current squared times resistance
• Energy


  Equal to power times time
• Energy


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


  In a fixed position, vibrate slightly