physics 1 energy

• What do stretched springs store ?

  Elastic potential energy
• What is the spring extension directly proportional to?

  The force
• What happens when the spring is stretched beyond the limit of proportionality?

  It won't be able to return to its normal shape
• What is specific heat capacity?

  The amount of energy required to increase the temperature of 1kg of a substance by 1oC
• What happens to 'dissipated' energy?

  It is lost to the surroundings
• differnece between an open and a closed system

  An open system can exchange energy and matter with its surroundings. A closed system cannot exchange energy or matter with the surroundings.
• What is the main energy transfer of a marathon runner?

  Chemical energy ➔ kinetic energy

  
  

  and also thermal
• Conduction primarily takes place in:

  solids
• How conduction works


  As one end of a solid object is heated, energy is transferred to the kinetic energy stores of the particles in that end.

  This causes the particles to vibrate faster, and so they collide with their neighbouring particles more often.

  As the collisions transfer kinetic energy, their neighbours also vibrate faster and collide more often with their neighbours.

  This process repeats over and over again so that energy is effectively passed along the object from one particle to the next.

  Even though it's kinetic energy that's being passed between particles, when considering the object as a whole we say that it's heat (or thermal energy) that's being transferred.
• What do we mean by the term 'fluid', and which states of matter are considered fluids?

  A fluid is a substance in which the particles are free to move around. They include both liquids and gases.
• what state can convection take place in

  liquids and gases
• How convection works


  As a fluid is heated the particles gain kinetic energy and spread further apart.

  This causes the fluid to become less dense and so it will rise above any cooler fluid that hasn't been heated (because that fluid is more dense).

  As the fluid cools down it will become more dense again, and so sink back down.

  If this process takes place in a limited space, like a container or a room, it can create a convection current.
• Which of the following examples help to reduce heat loss via convection :

  Covering yourself with a blanket at night

  
  

  Closing your windows
• When we say heat energy is transferred by 'radiation', we are referring to:

  Infrared radiation
• Do hotter or cooler objects emit more infrared radiation? and why

  Hotter objects have more energy, so also emit more energy.
• features of a house which help to reduce heat loss by conduction?

  Double glazed windows

  
  

  Cavity walls

  
  

  Walls made of a material with low thermal conductivity
• Single vs double glazing

  Single glazed windows only have one pane of glass, whereas double glazed windows have two panes of glass. In both cases, the panes of glass reduce heat loss by convection.

  
  

  The added benefit of double glazing is that there is a small air gap between the two panes of glass, which minimises conduction (as air is a poor conductor of heat).
• what is friction


  "The resistance that an object encounters when moving across a solid, or moving through a liquid"
• why are cars often streamlined

  Fast moving vehicles like cars and planes have a streamlined shape to reduce friction from air resistance. This allows them to use less fuel.
• what is power


  Power is the rate at which energy is transferred, or the rate at which work is done.
• what is work done

  The terms 'Work' or 'work done' refer to the energy transfered

  
  

  that occurs when a force is used to move an object by a certain distance
• unit for power


  Watts
• The government has recommended that the sale of filament lamps should be banned.

  
  

  Suggest why this is.

  Filament lamps are inefficient
• The main renewable energy resources are:

  Wind

  Solar

  Geothermal

  Water waves

  Biofuels

  Hydroelectricity

  Tidal
• Some of the main non-renewable energy resources are:

  Fossil fuels - resources such as coal, crude oil, and natural gas

  Nuclear energy
• Explain the difference between renewable and non-renewable energy resources. Use an example for each.

  Renewable energy resources are replenished

  Any renewable example explained

  Non-renewable energy resources are not replenished, and so have a limited supply

  Any non-renewable example explained

  
  

  A renewable energy resource is one that is being replenished as quickly as it is used. For example solar energy is renewable because new sunlight is always being generated by the sun - we don't use it up.

  
  

  A non-renewable energy resource on the other hand is one that isn't being replenished and so has a limited supply. For example fossil fuels like coal are non-renewable because they're not being replenished and at some point coal could run out.
• The pros and cons of fossil fuels

  Pros: Relatively Cheap in some places

  easy to extract

  high energy output

  
  

  Cons: Finite resource

  Produces CO2 and increase global warming
• The pros and cons of nuclear energy

  Pros:

  emits no pollutants

  can be used in any conditions

  unlikely to run out soon

  
  

  Cons:

  radiactive waste

  finite resource

  very expensive
• Give 3 disadvantages of nuclear power.

  Nuclear fuel is a finite resource

  It produces radioactive waste, which is harmful and lasts a long time

  It is expensive

  There is a small risk of a nuclear meltdown/accident

  There is a long start-up time for producing Nuclear energy

  nuclear power plants take many years to build
• how does wind power produce electricity


  Wind power is generated by wind turbines which have blades that spin due to the wind. This spinning action turns a generator which produces electricity.

  
  

  Wind turbines convert the kinetic energy from the wind into electrical energy.
• The pros of solar and wind power are:

  low running costs

  dont produce any pollutatnts whilst operating
• The cons of solar and wind power are:

  They have relatively high upfront costs

  Their power production is dependent on the weather, and therefore inconsistent

  They take up a lot of land space
• what is geothermal energy

  Geothermal energy is the thermal energy generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and the radioactive decay of materials like uranium deep in the Earth.
• how to georthermal powerstations work

  In regions with lots of volcanic activity, the ground is naturally very hot.

  So when we pump cold water down into the ground it will be heated by the hot rocks.

  If we pump this hot water back up to the surface we can use it to heat our homes.

  Alternatively, we let it heat up so much that it evaporates into steam.

  The steam can then be used to turn a turbine, which in turn can drive a generator to produce electricity.
• what are biofuels


  Biofuels are mostly made from recently living organisms, such as plants and algae. But they can also be formed from animal waste.

  
  

  This is in contrast to fossil fuels, which are made from organisms which died millions of years ago.

  
  

  In both cases though, plants and algae can trap the suns energy as part of photosynthesis, and this energy is released when we combust the fuel.
• What do we mean when we say that 'biofuels are carbon neutral'?

  They absorb the same amount of carbon dioxide while growing, as they release when they're burned
• In theory biofuels should be carbon neutral, but in reality they are not.

  
  

  Why is this?

  In order to grow the biofuels, we often have to clear land by cutting down trees. This means the trees can no longer photosynthesise and absorb CO2 themselves, and will also release large amounts of CO2 if burned.

  
  

  In addition, it usually requires a lot of energy to harvest, process, and transport the biofuels, which itself will produce a lot of CO2.

  
  

  Trees may be cut down, so no longer absorb CO2

  Trees may be cut down, and will release CO2 if burned

  Energy will be required to harvest, process and transport the biofuels...

  ... which will release more CO2
• how do hydroelectric dams work

  As water flows downhill (e.g. from mountains), a hydroelectric dam will trap the water in a man made lake, which is also known as a reservoir.

  Then whenever water is released through the dam, it spins turbines which are connected to generators, and so produce electricity.

  The water can then return to the river on the downstream side of the dam.
• Energy transfer in hydroelectric dams and tidal barrages

  In both cases the water on the higher side of the dam or barrage contains lots of gravitational potential energy. Once the dam or barrage is opened, this energy is transferred to kinetic energy as the water rushes down to the lower side.

  
  

  As the waters moves past turbines, some of its kinetic energy is transferred to the turbines, causing them to start spinning. Generators can then use this energy to generate electrical power.
• Which energy transfer takes place as water flows from the higher side of a hydroelectric dam (or tidal barrage) to the lower side?

  gpe ---> kinetic