paper 1

• energy stores

  Thermal energy stores

  -Kinetic energy stores

  -Gravitational potential energy stores

  -Elastic potential energy stores

  -Chemical energy stores

  -Magnetic energy stores

  -Electrostatic energy stores

  -nuclear energy stores
• work done


  -work done is another way of saying energy transferred

  -Work can be done when current flows or by force moving an object

  -For example, the fraction between a car brakes and its wheels does work as the car slows down. It causes energy transfer from the wheels kinetic energy stores to the thermal energy store of the surroundings.
• equation for work done

  work done=forcexdistance
• kinetic energy

  -anything that moves has a kinetic energy store energy is transferred to this store when an object speeds up and is transferred away from this store when an object slows down
• specific heat capacity

  specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1°c
• conservation of energy principle

  Energy can be transferred usefully, stored or dissipated but can never be created or destroyed
• power 


  power is the rate of energy transfer or rate of doing work
• what is power measured in?

  watts
• power equations

  -power=energy transfered ÷ time

  -power=work done ÷ time
• conduction 


  conduction is the process where vibrating particles transfer energy to neighbouring particles
• convection 


  Convection is where energetic particles move away from hotter regions to cooler regions
• Lubrication

  -lubrication reduces frictional forces

  -for objects being rubbed together lubricants can be used to reduce the friction between the objects surfaces

  -they see usually liquids like oil
• insulation

  reduces the rate of Energy Transfer by Heating
• efficiency equations

  -efficiency=useful output energy transfer ÷ total input energy transfer

  OR

  -useful power output ÷total power input
• non-renewable energy resources 


  -these are resources that will run out one day and do damage to the environment however our reliable
• renewable energy sources 


  -these are resources that will never run out, most of them do damage to the environment but in less nasty way than non renewables however they didn’t provide as much energy and unreliable as they depend on the weather
• renewable energy resources


  -The Sun(solar)

  -Wind

  -Water waves

  -Hydroelectricity

  -Biofuel

  -Ties

  -geothermal
• non-renewable energy resources

  -coal

  -Oil

  -(natural) gas
• geothermal power

  uses energy from underground thermal energy stores it is reliable with a few environmental problems and can be used to generate electricity or heat buildings directly
• hydro electric power

  Transfers energy from the kinetic store of falling water

  It can provide immediate response to increase demand for electricity and is reliable except for drought
• biofuels

  renewable energy resources created from either plants products or animal dung they can be solid liquid or gas and can be burnt to produce energy or run cars in the same way as fossil fuels
• pros of biofuels

  -they are supposedly carbon neutral

  -they are supposedly reliable
• cons of biofuel

  -Expensive

  -people worry that growing crops for biofuels will mean there isn’t enough space or water to meet demands for crops grown for food

  -by making room for them to grow many species lose habitats

  -the decay and burning increases carbon dioxide
• current

  the greater the resistance across a component the smaller the current that flows through it(for a given potential difference across the component)
• total charge through a circuit depends on current and time 


  charge=current x time
• formula linking potential difference and resistance

  potential difference=current x resistance
• LDR

  a resistor that is dependant on the intensity of light, in dark light the resistance is the highest and it bright light resistance falls
• thermistor


  a temperature dependent resistor

  in hot conditions the resistance drops and in cool conditions it goes up
• series circuits

  -in series circuits the same current flows through all components

  -the size of of the current is determined by the total potential difference of the cells and the the total resistance of the circuit
• parallel circuits 


  -in parallel circuits, each component is separately connected to the +ve and the -ve of the supply(except ammeters which are always connected in the series)

  -if you remove or disconnect one of them it will hardly effect the others at all
• neutral wire

  -The neutral wire is blue and completes the circuit when the appliance is operating normally current flows through the live and neutral wires it is around 0v
• live wire

  The live wire is brown and provides the alternating potential difference(at around 230v) from the mains supply
• earth wire


  It is green and yellow and is protecting the wiring and for safety. It stops the appliance casing from becoming live,it usually doesn’t carry a current when there’s a fault it’s also at 0v
• The two types of electricity supplies

  -Alternating current

  -Direct current
• alternating current

  In alternating current supplies the current is constantly changing direction alternating current of produced by alternating potential different in which the positive and negative and keep alternating
• Direct current


  Direct current is occurring there is always flowing in the same direction as created by a direct potential difference
• Energy transferred

  -The total energy transferred by an appliance depends on how long the appliance is on for and its power
• equation for energy transferred

  Energy transferred = power x time
• potential difference 


  -when an electrical charge goes through a change in potential difference energy is transferred
• equation for energy transferred 


  e=Qv