Energy, Electricity

• kinetic energy = 1/2 x mass x velocity^2
• GPE = mass x gravitational field strength x height
• Elastic Potential = energy stored in stretched or squashed objects
• Thermal = Energy due to the temperature of the object
• Kinetic energy = Energy stored within moving objects
• Chemical energy is the energy stored in the bonds of molecules.
• Gravitational potential energy is the energy stored in an object due to its position above the ground
• nuclear energy is energy stored in the nucleus of an atom
• Changes in a material's temperature or state of matter are caused by changes to the internal energy
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen due to their higher surface area to volume ratio
• Examples of specific heat capacities:

  • Brick: 840 J/kg/°C
  • Copper: 385 J/kg/°C
  • Lead: 129 J/kg/°C
• Specific heat capacity of water is 4,200 joules per kilogram per degree Celsius (J/kg°C)
• Specific heat capacity is the energy required to raise one kilogram (kg) of a material by one degree Celsius (°C)
• Lead has a low specific heat capacity, so it warms up and cools down quickly

  • Bricks have a higher specific heat capacity than lead, so they take longer to heat up and cool down
• Example:

  How much energy is needed to raise the temperature of 3 kg of copper by 10°C?

  ΔEₜ = 3 × 385 × 10

  ΔEₜ = 11,550 J
• Calculating thermal energy changes:

  ΔEₜ = m × c × Δθ

  Where:

  • ΔEₜ is measured in joules (J)
  • m is measured in kilograms (kg)
  • c is measured in joules per kilogram per degree Celsius (J/kg°C)
  • Δθ is measured in degrees Celsius (°C)
• Example:

  How much energy is lost when 2 kg of water cools from 100°C to 25°C?

  ΔEₜ = 2 × 4,200 × (100 - 25)

  ΔEₜ = 630,000 J
• Example:

  How hot does a 3.5 kg brick get if it is heated from 20°C by 400,000 J (400 kJ)?

  Δθ = 136°C

  Final temperature = 156°C
• The higher the temperature difference between an object and its surrounding, the faster the temperature will change.
• Coal, crude oil and natural gas are all fossils fuels formed from plant material from millions of years ago.
• Energy ressources are the different ways of supplying a particular energy form
• Non-renewable resources cannot be replaced once they have been used up or depleted.
• Renewable resources can be replenished over time as long as they are not exploited at too fast a rate.
• Hydroelectric power uses water falling through dams to turn turbines which drive generators producing electricity.
• What are some resources that supply kinetic energy?

  Waves, tides, wind and falling water
• What are some resources that supple chemical energy?

  Food, oil, coal, gas, petrol, turf and wood
• What are energy resources needed for?

  Electricity
• What are examples of non-renewable energy sources?

  Coal, oil, natural gas, nuclear energy
• How is coal formed?

  Decomposition of dead Trees and ferns over millions of years.
• How are crude oil and natural gas formed?

  Dead marine organisms
• Coal, oil and gas are being used up much more quickly than they are being replaced.
• Fossil fuels store chemical energy
• How Is coal used to form electricity?

  Coal or gas is burned to produce steam. The steam is forced through a turbine, which is like a fan, and causes it to rotate. The rotating turbine turns a generator to generate electricity.
• Advantages of using fossil fuels to generate electricity

  cheap

  easy to obtain

  reliable
• Disadvantages of using fossil fuels

  they are non-renewable and will run out

  the release of carbon dioxide adds to green house effect and increases global warming

  causes pollution which could impact lung damage and breathing difficulties
• Kinetic energy = 1/2 mass x speed^2
• Speed = the square root ( 2 x kinetic energy/mass)
• Solar panels only produce electricity during daylight hours.
• The units for gravitation potential energy are joules
• Resistance is measured in ohms