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What is a system?
an object or group of objects
What happens when something changes in a system?
energy is transferred between its stores or to the surroundings
What is a closed system?
one where no energy can escape to or enter the surroundings where the total energy never changes
What is kinetic energy?
energy an object has because it is moving
What is gravitational potential energy?
energy an object has because of its height above the ground
What is elastic potential energy?
energy an elastic object has when it is stretched or compressed
What is thermal/internal energy?
energy an object has because of its temperature (the total kinetic and potential energy of the particles in the object)
What is chemical energy?
energy that can be transferred by chemical reactions involving foods, fuels, and the chemicals in batteries
What is nuclear energy?
energy stored in the nucleus of an atom
What is magnetic energy?
energy a magnetic object has when it is near a magnet or in a magnetic field
What is electrostatic energy?
energy a charged object has when near another charged object
How is energy transferred by heating?
energy is transferred from one object to another object with a lower temperature
How is energy transferred by waves / light and sound?
waves can transfer energy by radiation
How is energy transferred by electricity?
when an electric current flows it can transfer energy
How is energy transferred mechanically?
energy is transferred when a force moves or changes the shape of an object
Equation for gravitational potential energy (j)
mass (kg) x gravitational field strength (n/kg) x height (m)
Equation for kinetic energy (j)
½ x mass (kg) x (speed)2 (m/s)
What is power?
How much work is done (or how much energy is transferred) per second.
What is work done?
The same thing as energy transferred
What is the unit of power?
watt
1 watt equals what?
1 watt = i joule of energy transferred per second
Equation for power (w)
energy transferred (j) / time (s)
Equation for elastic potential energy (j)
0.5 (n/m) x spring constant x extension 2
What is useful energy?
Energy that is transferred to useful stores
What is wasted/dissipated energy?
Energy that is transferred to less useful stores
Is energy ever entirely transferred usefully?
No, some energy is always wasted
What does all energy eventually end up as?
transferred to the thermal energy stores of the surroundings
What causes energy to be wasted in machines and why?
work done against the force of friction because energy is transferred to the thermal store of the machine and its surroundings
What is lubrication?
a way of reducing unwanted energy transfer due to friction
What is streamlining?
a way of reducing energy wasted due to air resistance or drag in wayer
What is thermal insulation used for?
a way of reducing energy wasted due to heat dissipated to the surroundings
What is efficiency?
a measure of how much energy is transferred usefully
Equation for effiency?
useful power output (w) / total power input (w)
How to calculate efficiency as a percentage?
Multiply the result the above decimal calculation by 100
What does thermal conductivity tell you?
how quickly energy is transmitted through a material
How to reduce the rate of heat loss from buildings?
the thickness of the walls and roof and the thermal conductivity of its walls and roof
How does thermal conductivity affect heat loss?
lower thermal conductivity = lower rate of heat loss
What is a thermal insulator?
a material which has a low thermal conductivity
What does the energy transfer per second through a material depend on?
the material thermal conductivity, the temperature difference between the two sides of the material, the thickness of the material
What do we use energy resources for mainly?
generating electricity, heating, transport
Where does most of our energy come from?
fossil fuels
What is a non-renewable energy resource?
not replaced as quickly as they are used and will eventually run out
What are non-renewable energy resources?
coal, oil, natural gas, nuclear fission
What are renewable energy resources?
they can be replaced at the same time they are used and will not run out
What are renewable energy resources?
solar, hydroelectric, tidal, wave, wind, geothermal, biofuels
Main uses of coal?
generating electricity
Source of coal / oil / natural gas?
extracted from underground
Advantages of coal / oil / natural gas
enough available to meet current energy demands, reliable as supply can be controlled to meet demand, relatively cheap to extract and use
Disadvantages of coal / oil / natural gas
will eventually run out, release carbon dioxide when burned one of the main causes of climate change, release other polluting gases such as sulfur dioxide which causes acid rain oil spills in the oceans
What are the main uses of nuclear energy?
generating electricity
What is the source of nuclear energy?
mining naturally occurring elements such as uranium and plutonium
Advantages of nuclear energy?
no polluting gases or greenhouse gases produced, enough available to meet current energy demands, large amounts of energy transferred from a very small mass of fuel, reliable as supply can be controlled to meet demand
Disadvantages of nuclear energy?
produces nuclear waste, which is: dangerous, difficult and expensive to dispose of, stored for centuries before it is safe to dispose of and nuclear power plants are expensive to: build and run, and shut down
What is the main uses of solar energy?
generating electricity and heating
What is the source of solar energy?
sunlight transfers energy to solar cells or sunlight transfers energy to solar heating panels
Advantages of solar energy?
can be used in remote places, very cheap to run once installed, no pollution/greenhouse gases produced
Disadvantages of solar energy?
supply depends on weather, expensive to buy and install, cannot supply large scale demand
Main uses of hydroelectric energy?
generating electricity
Source of hydroelectric energy?
water flowing downhill turns generators
Advantages of hydroelectric energy?
low running cost, no fuel cost, reliable and supply can be controlled to meet demand
Disadvantage of hydroelectric energy?
expensive to build hydroelectric dams, flood a large area behind the dams, could flood a large area behind the dam destroying habitats and resulting in greenhouse gas production from rotting vegetation
Main uses of tidal energy?
generating electricity
Sources of tidal energy?
turbines on tidal barrages turned by water as the tide comes in and out
Advantages of wave energy?
predictable supply as there are always tides, can produce large amounts of electricity, no fuel costs,no pollution/greenhouse gases produced
Disadvantages of tidal energy?
tidal barrages change marine habitats and can harm animals, restrict access and can be dangerous for boats, are expensive to build and maintain, cannot control supply varies depending on time of the month
Main uses of wave energy?
generating electricity
Main source of wave energy?
flowing generators powered by waves moving up and down
Advantages of wave energy?
low running cost, no fuel costs, no pollution/greenhouse gases
Disadvantages of wave energy?
floating generators change marine habitats, can harm animals, restrict access and can be dangerous for boats, are expensive to build, install and maintain, dependent on the weather, cannot supply large scale demand
What are the main uses of wind energy?
generating electricity
What is the main source of of wind energy?
turbines turned by the wind
Advantages of wind energy?
low running cost, no fuel cost, no pollution/greenhouse gases produced
Disadvantages of wind energy?
supply depends on weather, large amounts of land needed to generate enough electricity for large scale demand, can produce noise pollution for nearby residents
Main uses of geothermal energy?
generating electricity, heating
Sources of geothermal energy?
radioactive substances deep within the Earth transfer heat energy to its surface
Advantages of geothermal energy?
low running cost, no fuel costs, no pollution/greenhouse gases produced
Disadvantages of geothermal energy?
expensive to set up, only possible in a few suitable locations around the world
Main uses of biofuels?
generating electricity, transport
Sources of biofuels?
fuel produced from living or recently living organisms, for example, plants and animal waste
What are the advantages of biofuels?
they can be carbon neutral, the amount of carbon dioxide released when the fuel is burnt is equal to the amount of carbon dioxide absorbed when the fuel is grown, reliable and supply can be controlled to meet demand
What are the disadvantages of biofuels?
expensive, growing biofuels requires a lot of land and water that could be used for food production, can lead to deforestation as forests are cleared for growing biofuel crops
