energy

• what are the 8 energy stores?

  magnetic, chemical, thermal, electrostatic, kinetic, elastic potential, gravitational potential, nuclear
• what is a system?

  a system is a group of objects or one object alone
• what is the equation for kinetic energy?

  kinetic energy = 0.5 x mass x speed squared
• how is elastic potential energy calculated?

  elastic potential energy = 0.5 x spring constant x extension squared
• how is gravitational energy measured?

  gravitational potential energy = mass x gravitational field strength x height
• what is specific heat capacity?

  specific heat capacity is the amount of energy required to raise the temperature of a 1 kg of a substance by 1 degree or 1 kelvin
• what is the specific heat capacity equation?

  change in internal energy= mass x specific heat capacity x temperature change
• what is the conservation of energy?

  Energy cannot be created or destroyed, only transferred or dissipated from one form to another.
• what is power?

  power is the rate of energy being transferred or the rate of work being done.
• how is energy transferred when an object is projected upwards?

  the force exerted by the person throwing the object does work. Energy is transferred from the chemical energy in the persons arm to the kinetic energy of the ball. Energy is transferred from kinetic energy to gravitational potential energy.
• what are the energy changes when an moving object hits an obstacle?

  the normal contact force between the moving object and obstacle does work. Energy is transferred from the the kinetic energy store of the moving object to the elastic potential energy of the moving object. Some energy is transferred as sound waves.
• what are the energy pathways?

  heating

  electrically

  radiation
• if motor a and b lift the same weight, but motor a does it faster , which motor is more poweful?

  motor a is mor powerful because energy is transferred over a smaller amount of time, making it more powerful.
• what can happen to energy and what cant?

  energy can be transferred usefully

  energy can be dissipated

  energy can be stored

  energy cannot be created

  energy cannot be destroyed
• what is the net change in energy in a closed system?

  the net change in energy in a closed system is zero
• what is conduction?

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

  convection is where particles which energy move away from hotter to colder region
• describe the process of conduction

  when a substance is heated, particles vibrate and collide with each other. this continues throughout the object
• where does conduction take place?

  conduction takes place in solids
• describe the process of convection

  when a substance is heated, warmer particles rise to the top as they are less dense. these warm particles cool down and become denser, sinking back down.
• where does convection take place?

  convection takes place in liquids and gases
• what is thermal conductivity?

  thermal conductivity is how quickly energy is transferred through a material through conduction
• what does a higher thermal conductivity mean?

  high thermal conductivity means the solid transfer energy through conduction quickly
• how does lubrication stop unwanted energy transfers?

  lubricants reduce friction between object surfaces when they move together. Friction causes some energy to be dissipated
• how do thick walls with low thermal conductivity reduce unwanted energy transfers?

  The thicker the walls and the lower the thermal conductivity, the slower the rate of energy transfer so the slower the building will cool down and conserve more energy
• how do cavity walls reduce unwanted energy transfers?

  cavity walls are two walls with an air gap in between which reduces energy lost by conduction as air is a poor conductor of heat
• how does cavity wall insulation reduce unwanted energy transfers?

  cavity wall insulation fills the air gap between cavity walls. this reduces energy lost by convection
• how can loft insulation reduced unwanted energy transfers?

  loft insulation reduces convection currents in lofts
• how do double glazed windows reduce unwanted energy transfers?

  double glazed windows have two panes of glass which reduces energy lost by convection. they also have an air gap which reduces enrgy lost by conduction as air is poor conductor of heat
• how do draught excluders reduce unwanted energy transfers?

  draught excluders reduce energy lost by convection
• what is the equation for efficiency?

  Efficiency = (Useful output / Total input) x 100%
• how can we make something more efficient?

  Streamlining, insulating objects and lubrication is some of the ways to make something more efficient
• why is nothing 100% efficient?


  all energy ends up transferred into thermal energy stores
• the less energy wasted, the more efficient the system is
• what are fossil fuels and what are the 3 main types ?

  1. Coal 2. Oil 3. Natural gas

  fossil fuels are hydro carbons