physics paper 1 eneryg

• Types of energy store

  Kinetic

  Thermal

  Chemical

  Gravitational potential

  Elastic potential

  Electrostatic

  Magnetic

  Nuclear
• A system


  a single object or group of objects you're interested in
• Closed systems


  Neither matter or energy can leave

  Net change in total energy is always 0
• What happens when a system changes?

  energy is transferred

  Can be transferred into or away from system, between objects in the system or between energy stores
• Energy transfer in a kettle

  Energy transferred to water from the heating element by heating, into the water's thermal energy store causing temperature to rise
• Energy transfers


  Electrically

  mechanically

  by heating

  By radiation
• Work done is also what?

  energy transferred
• How can work be done?

  when a current flows against resistance in a circuit

  by a force moving an object
• Energy transfers to and from Ek stores


  transferred to when object speeds up and away when an object slows down
• Formula for Kinetic energy


  1/2 x Mass (kg) x speed (m/s)²
• Formula for gravitational potential energy (Ep)


  mass (kg) x gravitational field strength (N/kg) x height (m)
• What rule ling Ek and Ep?

  energy lost from g.p.e store = Energy gained in Ek store
• What acts against all falling objects

  air resistance

  Causes some energy t be transferred to other stores e.g. thermal
• What transfers energy to an objects elastic potential store (Ee)

  stretching or compressing
• Formula for Ee

  Ee= 1/2 x spring constant (N/m) x extension (m)²
• When does the formula for Ee not work?

  when limit of proportionality has been exceeded
• What is specific heat capacity?

  amount of energy needed to rise the temperature of 1kg of substance by 1°C
• What's the formula for specific heat capacity?

  ∆E (change in thermal energy j)= mass (kg) x specific heat capacity (J/Kg°C) x∆θ (temp change °C)
• conservation of energy principle


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


  the rate of energy transferred or the rate of doing work
• What does one watt equal?

  1 joule of energy transferred per second
• Formulas for power


  p= energy transferred/ time (s) OR p=work done/ time (s)
• What is a powerful machine?

  one that transfers lots of energy in short space of time
• What is conduction?


  process where vibrating particles transfer energy to their neighbouring particles
• What happens during conduction?

  Energy is transferred by heating to the thermal store of an object. This energy is shared out across the kinetic energy stores of the particles in the object.

  Particles in area being heated vibrate more an collide w/ each other.

  Collisions cause energy to be transferred between particle Ek store.

  Process continues throughout object until energy is transferred to other side.

  Energy then usually transferred to thermal energy store of surroundings
• What is thermal conductivity

  measure of how quickly energy is transferred through a material by conduction

  High thermal conductivity= energy transferred quickly
• Convection


  energetic particles move away from hotter to colder regions
• Where does convection happen

  gases and liquids because the particles are able to move
• What happens during convection?

  Energy is transferred to the thermal energy store of liquid or gas and this energy is transferred across Ek store of its particles.

  The particles move faster causing the space between individual particles to increase causing the density to decrease.

  The less dense region will rise above the denser, cooler region.

  If constant heat source a convection current is created.
• Convection current of a radiator

  Energy transferred from radiator to nearby air particles by conduction.

  Air by radiator becomes warmer and less dense so rises and is replaced by cooler air.

  Cooler air then heated by the radiator.

  At the same time previously heated air transfers energy to surroundings so cools and sinks.

  Repeats creating convection current
• When something moves, what force is usually there?

  there is usually a frictional force acting against it which causes some energy to be dissipated.
• What can be used to reduce friction?

  lubricants

  Usually liquids like oil so they can flow easily between objects and coat them.
• 2 ways to prevent energy loss through heating in a home

  thick walls made from materials w/ low thermal conductivity

  Use thermal insulation
• Examples of thermal insulation


  cavity walls

  cavity wall insulation

  loft insulation

  Double-glazed windows

  Draught excluders
• Cavity walls


  made up of inner and outer wall with air gap in-between to decrease heat loss from conduction.

  Cavity wall insulation is where air gap is filled with foam so reducing energy loss by convection
• Loft insualtion


  fibreglass wool laid across floor of loft to reduce energy lost by convection from stopping convection currents forming.
• Double- glazed windows


  air gap between two sheets of glass to prevent energy transfer by conduction
• Draught excluders


  around doors and windows to decrease energy transfers by convection.
• How can the efficiency of an object be improved?

  insulating

  lubricating

  making more streamlined
• How to work out efficiency?

  useful output/ total input