Section 4: Energy resources and energy transfer
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a) Units
4.1: Use the following units: kilogram (kg), joule (J), meter (m), meter/second (m/s), meter/second² (m/s²), newton (N), second (s), watt (W)
Kilogram: Used to measure mass
Joule: Used to measure amount of energy
Meter: Used to measure distance
Meter per second: Used to measure distance in a given period of time
Meter per second squared: Used to measure acceleration
Newton: Used to measure force
Second: Used to measure time
Watt: Used to measure amount of energy in a given period of time
Kilogram: Used to measure mass
Joule: Used to measure amount of energy
Meter: Used to measure distance
Meter per second: Used to measure distance in a given period of time
Meter per second squared: Used to measure acceleration
Newton: Used to measure force
Second: Used to measure time
Watt: Used to measure amount of energy in a given period of time
b) Energy transfer
4.2: Describe energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear, and potential (elastic and gravitational)
Energy frequently changes from one form to another. Some examples of this include:
Energy frequently changes from one form to another. Some examples of this include:
- Electrical energy being converted to heat energy in a house's central heating
- Electrical energy being converted to light energy when the lights are turned on
- Chemical energy being converted to kinetic energy during exercise
- Nuclear energy being converted to heat energy and kinetic energy in a nuclear explosion
- Elastic potential energy being converted to kinetic energy in archery
4.3: Understand that energy is conserved
The Law of Conservation of Energy states that energy cannot be created or destroyed in any process. Therefore it can only transferred and can also be conserved.
The Law of Conservation of Energy states that energy cannot be created or destroyed in any process. Therefore it can only transferred and can also be conserved.
4.4: Know and use the relationship between efficiency and energy output
Efficiency = useful energy output / total energy input
Efficiency = useful energy output / total energy input
4.5: Describe a variety of everyday scientific devices and situations, explaining the fate of input energy in terms of the above relationship, including their representation by Sankey diagrams
Sankey diagrams can be used to show how energy is transferred and converted. They show how the input energy is used and the efficiency of the device can be calculated using a Sankey diagram. For example:
Sankey diagrams can be used to show how energy is transferred and converted. They show how the input energy is used and the efficiency of the device can be calculated using a Sankey diagram. For example:
In the above Sankey diagram, the energy transfers into and out of a filament lamp are shown. The light energy is the useful part of the transfer; the filament lamp is used for lighting up the surroundings. The rest of the heat energy is transferred to surroundings and is wasted. As shown above, the width of the arrows is directly proportional to the amount of energy.
4.6: Describe how energy transfer may take place conduction, convection and radiation
Heat energy can be transferred via conduction, convection or radiation.
Conduction
Most metals are good conductors of electricity and heat. Conduction is the transfer of heat/thermal energy through a substance without the substance itself moving.
Heat energy can be transferred via conduction, convection or radiation.
Conduction
Most metals are good conductors of electricity and heat. Conduction is the transfer of heat/thermal energy through a substance without the substance itself moving.
Convection
Liquids and gases are fluids - the particles in them can move from one place to another. Convection occurs when the particles with more heat energy move to a place where there are particles with less heat energy. Heat energy is transferred from hot places to cool places by convection. The fluid in a hot area is less dense than in a cold area, so it rises to the cold areas. Convection currents transfer heat in this way.
Radiation
All objects give off infrared radiation. The hotter an object is, the more radiation it emits. Infrared radiation is part of the electromagnetic spectrum, so it can travel through a vacuum: this is why we can feel the sun's heat on earth. Thin, flat objects radiate heat energy faster than a thicker object. Lighter objects reflect heat and darker objects absorb heat.
Liquids and gases are fluids - the particles in them can move from one place to another. Convection occurs when the particles with more heat energy move to a place where there are particles with less heat energy. Heat energy is transferred from hot places to cool places by convection. The fluid in a hot area is less dense than in a cold area, so it rises to the cold areas. Convection currents transfer heat in this way.
Radiation
All objects give off infrared radiation. The hotter an object is, the more radiation it emits. Infrared radiation is part of the electromagnetic spectrum, so it can travel through a vacuum: this is why we can feel the sun's heat on earth. Thin, flat objects radiate heat energy faster than a thicker object. Lighter objects reflect heat and darker objects absorb heat.
4.7: Explain the role of convection in everyday phenomena
Heat energy can be transferred through houses via convection. For example, radiators use convection currents to transfer the thermal energy that they emit evenly throughout the house. Also, warm surface air rises into the atmosphere via convection currents.
Heat energy can be transferred through houses via convection. For example, radiators use convection currents to transfer the thermal energy that they emit evenly throughout the house. Also, warm surface air rises into the atmosphere via convection currents.
4.8: Explain how insulation is used to reduce energy transfers from buildings and the human body
Heat can be lost from a building in many different ways, for example, through the roof, windows, walls, floor, and the gaps in the door. Insulation is used to reduce heat loss. Double glazed windows (two glass panes with air in between) can be used in order to reduce heat loss through conduction because air is a poor conductor of heat. Walls and roofs can be insulated by blowing insulating material into gaps (such as door draft excluders to reduce convection). Loft insulation can also be used for roofs.
In humans, heat loss by conduction can be reduced by wearing an insulating material (wool, fur, feathers, down), which can be found in jackets. This also prevents heat loss by convection because the heated particles cannot escape into the air. Divers also wear wetsuits in order to reduce heat loss. A wetsuit traps an insulating layer of water between the wetsuit and the diver's body.
Heat can be lost from a building in many different ways, for example, through the roof, windows, walls, floor, and the gaps in the door. Insulation is used to reduce heat loss. Double glazed windows (two glass panes with air in between) can be used in order to reduce heat loss through conduction because air is a poor conductor of heat. Walls and roofs can be insulated by blowing insulating material into gaps (such as door draft excluders to reduce convection). Loft insulation can also be used for roofs.
In humans, heat loss by conduction can be reduced by wearing an insulating material (wool, fur, feathers, down), which can be found in jackets. This also prevents heat loss by convection because the heated particles cannot escape into the air. Divers also wear wetsuits in order to reduce heat loss. A wetsuit traps an insulating layer of water between the wetsuit and the diver's body.
c) Work and power
4.9: Know and use the relationship between work, force and distance moved in the direction of the force
Work done = force x distance moved
W = F x d
Work done = force x distance moved
W = F x d
4.10: Understand that work done is equal to energy transferred
"Work done" is simply another way of saying "energy transferred" (i.e. W = E)
"Work done" is simply another way of saying "energy transferred" (i.e. W = E)
4.11: Know and use the relationship between gravitational potential energy, mass, gravity and height
Gravitation potential energy = mass x gravity x height
GPE = m x g x h
Gravitation potential energy = mass x gravity x height
GPE = m x g x h
4.12: Know and use the relationship between kinetic energy, mass and speed
Kinetic energy = 1/2 x mass x speed2
KE = 1/2 x m x v2
4.13: Understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work
The Law of Conservation of Energy states that the work done is equal to the energy transferred. This can be shown by the following equation:
Work done = kinetic energy - potential energy
The Law of Conservation of Energy states that the work done is equal to the energy transferred. This can be shown by the following equation:
Work done = kinetic energy - potential energy
4.14: Describe power as the rate of transfer of energy or the rate of doing work
Power is a measure of how quickly work can be done or energy can be transferred. A more powerful person can do the same amount of work in a shorter period of time.
Power is a measure of how quickly work can be done or energy can be transferred. A more powerful person can do the same amount of work in a shorter period of time.
4.15: Use the relationship between power, work done (energy transferred) and time taken
Power = work done / time taken
P = W / t
Power = work done / time taken
P = W / t
d) Energy resources and electricity generation
4.16: Describe the energy transfers involved in generating electricity using different methods
- wind - kinetic energy from the wind turns a turbine which turns a generator that produces electrical energy
- water (hydroelectricity) - kinetic energy from falling water with GPE turns a turbine which turns a generator that produces electricity
- geothermal resources - thermal energy evaporates water and the resulting steam turns a turbine which turns a generator that produces electrical energy
- solar heating systems - heat energy from the sun heats water to create hot water
- solar cells - light energy from the sun shines on solar cells which convert it to electrical energy
- fossil fuels - chemical energy is burnt to form heat energy which evaporates water and the resulting steam turns a turbine which turns a generator that produces electrical energy
- nuclear power - nuclear energy from uranium is converted to kinetic energy which turns turbines
4.17: Describe the advantages and disadvantages of methods of large-scale electricity production from various renewable and non-renewable resources
- Geothermal energy is renewable, but is only accessible in places where volcanic activity is frequent
- Solar heating is renewable, but is expensive to set up and is dependent on the weather
- Controlled nuclear fission is non-renewable, but can be used to produce near limitless amounts of clean heat energy; however, there are problems with storing radioactive waste
- Fossil fuels are non-renewable, and produce greenhouse gases
- Hydroelectricity is renewable and produces no greenhouse gases
- Tidal power is renewable and produces no greenhouse gases
- Wind power is renewable and produces no greenhouse gases
- Solar power is renewable and produces no greenhouse gases, however is very expensive to set up