AQA
ENERGY – part 1
Energy Conservation and Dissipation
Energy stores and changes
System | An object or group of objects that interact together | EG: Kettle boiling water. |
Energy stores | Kinetic, chemical, internal (thermal), gravitational potential, elastic potential, magnetic, electrostatic, nuclear | Energy is gained or lost from the object or device. |
Ways to transfer energy | Light, sound, electricity, thermal, kinetic are ways to transfer from one store to another store of energy. | EG: electrical energy transfers chemical energy into thermal energy to heat water up. |
Unit | Joules (J) |
Efficiency = Useful output energy transfer
Total input energy transfer
Efficiency = Useful power output
Total power input
HIGHER: efficiency can be increased using machines.
Prefix | Multiple | Standard form |
Kilo | 1000 | 103 |
Mega | 1000 000 | 106 |
Giga | 100 000 000 | 109 |
| Units |
Specific Heat Capacity | Joules per Kilogram degree Celsius (J/Kg°C) |
Temperature change | Degrees Celsius ( °C) |
Work done | Joules (J) |
Force | Newton (N) |
Distance moved | Metre (m) |
Power | Watts (W) |
Time | Seconds (s) |
Kinetic energy | Energy stored by a moving object | ½ X mass X (speed)2 ½ mv2 |
Elastic Potential energy | Energy stored in a stretched spring, elastic band | ½ X spring constant X (extension)2 ½ ke2 (Assuming the limit of proportionality has not been exceeded) |
Gravitational Potential energy | Energy gained by an object raised above the ground | Mass X gravitational field strength X height mgh |
Dissipate | To scatter in all directions or to use wastefully | When energy is ‘wasted’, it dissipates into the surroundings as internal (thermal) energy. |
Work | Doing work transfers energy from one store to another | By applying a force to move an object the energy store is changed. | Work done = Force X distance moved W = Fs |
Power | The rate of energy transfer | 1 Joule of energy per second = 1 watt of power | Power = energy transfer ÷ time P = E ÷ t Power = work done ÷ time, P = W ÷ t |
Energy pathways
Mechanical | Force acts upon an object |
Electrical | Electric current flow |
Heat | Temperature difference between objects |
Radiation | Electromagnetic waves or sound |
Efficiency | How much energy is usefully transferred |
Change in thermal energy = mass X specific heat capacity X temperature change
∆E= m X c X ∆θ
Specific Heat Capacity | Energy needed to raise 1kg of substance by 1°C | Depends on: mass of substance, what the substance is and energy put into the system. |
Principle of conservation of energy | The amount of energy always stays the same. | Energy cannot be created or destroyed, only changed from one store to another. |
| Units |
Energy (KE, EPE, GPE, thermal) | Joules (J) |
Velocity | Metres per second (m/s) |
Spring constant | Newton per metre (N/m) |
Extension | Metres (m) |
Mass | Kilogram (Kg) |
Gravitational field strength | Newton per kilogram (N/Kg) |
Height | Metres (m) |
Reducing friction - using wheels, applying lubrication. Reducing air resistance – travelling slowly, streamlining.
Frictional forces cause energy to be transferred as thermal energy. This is wasted.
HIGHER: When an object is moved, energy is transferred by doing work.
Closed system | No change in total energy in system |
Open system | Energy can dissipate |
Useful energy | Energy transferred and used |
Wasted energy | Dissipated energy, stored less usefully |
Work done = Force X distance moved
Ways to reduce ‘wasted’ energy | Energy transferred usefully | Insulation, streamline design, lubrication of moving parts. |
AQA
ENERGY – part 2
Non-renewable energy resource | These will run out. It is a finite reserve. It cannot be replenished. | e.g. Fossil fuels (coal, oil and gas) and nuclear fuels. |
Renewable energy resource | These will never run out. It is an infinite reserve. It can be replenished. | e.g. Solar, Tides, Waves, Wind, Geothermal, Biomass, Hydroelectric |
Power station – NB: You need to understand the principle behind generating electricity. An energy resource is burnt to make steam to drive a turbine which drives the generator.
National Grid
Global Energy Resources
Energy resource | How it works | Uses | Positive | Negative |
Fossil Fuels (coal, oil and gas) | Burnt to release thermal energy used to turn water into steam to turn turbines | Generating electricity, heating and transport | Provides most of the UK energy. Large reserves. Cheap to extract. Used in transport, heating and making electricity. Easy to transport. | Non-renewable. Burning coal and oil releases sulfur dioxide. When mixed with rain makes acid rain. Acid rain damages building and kills plants. Burning fossil fuels releases carbon dioxide which contributes to global warming. Serious environmental damage if oil spilt. |
Nuclear | Nuclear fission process | Generating electricity | No greenhouse gases produced. Lots of energy produced from small amounts of fuel. | Non-renewable. Dangers of radioactive materials being released into air or water. Nuclear sites need high levels of security. Start up costs and decommission costs very expensive. Toxic waste needs careful storing. |
Biofuel | Plant matter burnt to release thermal energy | Transport and generating electricity | Renewable. As plants grow, they remove carbon dioxide. They are ‘carbon neutral’. | Large areas of land needed to grow fuel crops. Habitats destroyed and food not grown. Emits carbon dioxide when burnt thus adding to greenhouse gases and global warming. |
Tides | Every day tides rise and fall, so generation of electricity can be predicted | Generating electricity | Renewable. Predictable due to consistency of tides. No greenhouse gases produced. | Expensive to set up. A dam like structure is built across an estuary, altering habitats and causing problems for ships and boats. |
Waves | Up and down motion turns turbines | Generating electricity | Renewable. No waste products. | Can be unreliable depends on wave output as large waves can stop the pistons working. |
Hydroelectric | Falling water spins a turbine | Generating electricity | Renewable. No waste products. | Habitats destroyed when dam is built. |
Wind | Movement causes turbine to spin which turns a generator | Generating electricity | Renewable. No waste products. | Unreliable – wind varies. Visual and noise pollution. Dangerous to migrating birds. |
Solar | Directly heats objects in solar panels or sunlight captured in photovoltaic cells | Generating electricity and some heating | Renewable. No waste products. | Making and installing solar panels expensive. Unreliable due to light intensity. |
Geothermal | Hot rocks under the ground heats water to produce steam to turn turbine | Generating electricity and heating | Renewable. Clean. No greenhouse gases produced. | Limited to a small number of countries. Geothermal power stations can cause earthquake tremors. |
Transport | Petrol, diesel, kerosene produced from oil | Used in cars, trains and planes. |
Heating | Gas and electricity | Used in buildings. |
Electricity | Most generated by fossil fuels | Used to power most devices. |
Using fuels
Energy resources
Power station | Generates electricity | Fuel burnt releasing thermal energy | Water boils into steam | Steam turns turbine | Turbine turns generator | Generator induces voltage |
National Grid | Transports electricity across UK | Power station | Step-up transformer | Pylons | Step-down transformer | House, factory |
Energy demand is increasing as population increases.
Renewable energy makes up about 20% of energy consumption.
Fossil fuel reserves are running out.
Using renewable energy will need to increase to meet demand.