physics double aqa

• what is a system?

  object or group of objects
• what is energy measured in?

  Joules
• 4 energy stores

  Kinetic, Gravitational, Elastic Potential and Thermal energy
• what is specific heat capacity?

  the amount of energy required to raise the temperature of one kilogram of the substance by one degree C
• what is power?

  the rate at which energy is transferred or the rate at which work is done
• what is power measured in?

  Watts
• GPE and KE in terms of a closed system

  more GPE at the top and less KE at the top = less GPE at the bottom and more KE at the bottom
• law of conservation of energy

  Energy cannot be created nor destroyed, it can only be stored or dissipated
• closed system

  no energy is transferred to or from the surroundings
• how to conserve thermal energy in a house?

  using insulation such as double glazing windows and cavity walls
• 2 non-renewable energy sources?

  Fossil fuels (oil, natural gas and coal used to make steam for generators and turbines)

  Nuclear fuel (uranium used in nuclear reactors for heat)
• 4 renewable energy sources

  Wind power (has kinetic energy for turbines)

  Hydroelectric (water behind dams have GPE which falls through turbines)

  Solar (light from the sun produces electricity)

  Biofuel (plant matter burned to produce heat)
• what is electricity?


  the flow of charge, that utilises electrons to carry energy from one source to a component where the energy is relased
• what is potential difference?

  a measure of how much energy is transferred to/ each coulomb of charge
• what is potential difference measured in?

  coulombs
• what is charge measured in?

  volts
• what is current?

  the rate of flow of charge
• what is charge measured in?

  amperes
• symbol for an open switch

  open switch

  
• symbol for an ammeter

  always connected in series with components

  
• symbol for a voltmeter

  always in parallel to the components your measuring the voltage of

  
• symbol for a fuse

  fuse

  
• symbol for an LED

  LED

  
• symbol for a thermistor

  thermistor

  
• symbol for a cell

  cell

  
• symbol for a lamp

  lamp

  
• symbol for a LDR

  LDR

  
• symbol for a battery

  battery

  
• symbol for a fixed resistor

  fixed resistor

  
• symbol for a variable resistor

  variable resistor

  
• symbol for a diode

  diode

  
• what is resistance?


  the measure of how much a component resists the flow of current
• what is resistance measure in?

  ohms
• ohmic conductor graph

  measures how much current varies with PD for a component when using a variable resistor in series to charge its PD, V and I are directly proportionate

  
• filament lamp graph


  resistance is not constant as delocalised electrons collide with the Ionic lattice which causes them to vibrate more so temperature increases so a larger current = larger resistance

  
• diode graph

  diode only lets current flow in one direction, low resistance is forward and high resistance is reverse direction

  
• series circuits

  Total PD is shared between all components

  current is the same for all components

  total resistance = sum of all resistances
• parallel circuits

  PD for each branch = pd for cell/ battery

  current is split between branches

  adding more resistors in parallel reduces the total resistance
• thermistor

  if temperature increases = resistance decreases
• Light-dependent resistor

  if light intensity increase = resistance decreases