Efficiency Flashcards
What causes a rise in temperature!?
A rise in temperature is caused by the transfer of wasteful energy in mechanical processes. The energy is dissipated into the system.
How is energy dissipated in a mechanical system!?
when two surfaces rub together. Work is done against friction which causes heating of the two surfaces – so the internal (thermal) energy store of the surfaces increases and this is then transferred to the internal energy store of the surroundings.
What energy is useful when using an electric kettle!?
Energy used to heat the water
What is energy wasted on when using an electric kettle!?
Internal (thermal) energy heating the kettle. Infrared radiation transferred to the surroundings
How is energy used usefully when using a hair dryer!?
Internal (thermal) energy heating the air. Kinetic energy of the fan that blows the air.
How is energy wasted when using a hair dryer!?
Sound radiation. Internal (thermal) energy heating the hairdryer. Infrared radiation transferred to the surroundings
How is energy used usefully when using a light bulb!?
Light radiation give out by hot filament
How is energy wasted when using a light bulb!?
Infrared radiation transferred to the surroundings
How is energy used usefully when using a TV!?
Light radiation that allows the image to be seen. Sound radiation that allows the audio to be heard
How is energy wasted when using a TV!?
Internal (thermal) energy heating the TV set. Infrared radiation transferred to the surroundings
How are some devices made in terms of there energy wastage !?
Devices can be made to reduce the energy that they waste or ‘dissipate’ to the surroundings.
Name one example that a device has been made with energy wastage in mind….
One example is lubrication being used to reduce the friction between moving parts of a machine. This reduces the thermal energy transferred.
How can energy wastage be reduced with products that are made to produce kinetic energy!?
For systems that are designed to transfer thermal energy, the wasteful dissipation of thermal energy to the surroundings can also be reduced. This is often done by using thermal insulation,
Name an example of how energy wastage has been improved for products that are designed to produce thermal energy….
for example, making a kettle from plastic, which is a thermal insulator
Devices are designed to waste as little energy as possible meaning that…..
As much of the input energy as possible should be transferred into useful energy stores
A very efficient devise will waste what!?
Very little of its input energy
A very inefficient device will waste…..
Most of its input energy
What is efficiency?
The fraction of the energy supplied to a device which is transferred in a useful form.
What is the efficiency of a device?
The efficiency of a device is the proportion of the energy supplied that is transferred in useful ways.
How can efficiency be calculated in?
The efficiency can be calculated as a decimal or a percentage.
What is the equation for efficiency?
Efficiency= useful energy transferred/ total energy supplied
What are both useful energy transferred and total energy supplied measured in?
They are both measured in joules (J)
What does it mean when the energy is dissipated?
The spreading out and transfer of energy stores into less useful forms, such as thermal energy causing the surroundings to heat up. Dissipated energy is often referred to as ‘wasted’ energy, since it is not transferred to a useful output.
What is it impossible for efficiency to be?
Greater than 1 or an efficiency percentage greater than 100%.
What would it mean if the efficiency was greater than 1 or 100%?
It would mean that more energy is transferred than being supplied which would mean that energy would be created.
What law would it break if the efficiency was greater than 1 or 100%?
This would break the law of conservation of energy.
Why do devices waste energy?
Devices waste energy for various reasons, including friction between their moving parts, electrical resistance, and unwanted sound energy.
What is useful to do with efficiency?
In general, it is useful to increase the efficiency of any process or device
How can you increase the efficiency of any process or device?
This can be achieved by reducing wasted energy transfers so more of the input energy is usefully transferred.
How can mechanical devices become more efficient?
Mechanical devices can be made more efficient through
lubrication
to reduce the friction between moving parts of a machine and increase the amount of useful energy transferred
What is lubrication?
Liquid used to reduce friction
How can the efficiency be improved for systems that are designed to transfer thermal energy?
the efficiency can be improved by reducing the wasteful dissipation of thermal energy to the surroundings, for example by using insulation.
Why is Efficient heating of buildings important?
Efficient heating of buildings is important in reducing the amount of energy used, This is because the amount of energy required for heating can be very large
How will energy transfer inside warm buildings?
Thermal energy will transfer from inside warm buildings to the cooler surroundings outside, so reducing this thermal energy transfer is important.
What are the poor conductors of heat?
When trying to keep houses warm, the choice is between materials that are poor
conductors
such as brick, wood, plastic and glass.
What is a conductor?
An electrical conductor is a material which allows an electrical current to pass through it easily. It has a low resistance.
Why would a copper house be cold to live in?
house built of conducting materials like copper would be very cold to live in, as energy would be able to leave the house easily.
What is thermal Conductivity a measure of?
Thermal conductivity
is a measure of how well a material conducts energy when it is heated.
What is thermal conductivity?
A measure of how well a material conducts energy when it is heated.
What is the thematic conductivity of copper?
385 watts per meter per degree Celsius (W/m/°c)
What is the thermal conductivity of glass?
watts per metre per degree Celsius (W/m/°C)) 0.170
What is the thermal conductivity of brick?
(watts per metre per degree Celsius (W/m/°C))
What is the thermal conductivity of air?
(watts per metre per degree Celsius (W/m/°C))
How is thermal energy transferred reduced in a warm house?
To reduce thermal energy transferred from a warm house, the walls can be built thicker, so the energy must travel further before it is transferred to the outside
How can thermal energy transfers be further reduced (not thicker walls!!)
Thermal energy transfers can be reduced further if there are two walls with an air gap between them, as air has a lower
thermal conductivity
than brick. This is known as a ‘cavity wall’.
Name a way to use energy….
Nearly everything requires
energy
and a way to use energy is by transferring it from one
energy store
to another
What is an energy store?
The different ways in which energy can be stored,
Name 5 examples of an energy store…..
including chemical, kinetic, gravitational potential, elastic potential and thermal stores.
What are energy resources?
Useful supply or store of energy.
Name the 9 major energy resources available to produce electricity…..
fossil fuels
nuclear fuel
biofuel
wind
hydroelectricity
geothermal
tidal
water waves
the Sun.
What are fossil fuels?
Natural, finite fuel formed from the remains of living organisms, eg oil, coal and natural gas.
What is nuclear fuel?
Radioactive materials, usually uranium or plutonium, used in nuclear reactors.
What is wind power?
Energy generated from the moving air.
What is hydroelectricity?
Electricity that is generated by the movement of water
What is geothermal?
Energy from the heat of the Earth
What is 4 main ways energy needed for?
Homes
Public services
Factories and farms
Transport
Name 3 examples of ways energy is used in homes
Cooking
Heating
Running appliances
Name 4 examples of ways that energy is needed for public services ….
Schools and hospitals-Running machinery and warming rooms
Name 4 examples of ways that energy is needed for public transport….
buses, trains, cars and boats all need a fuel source, and some trains and trams connect to an electricity supply
Name 4 examples of ways that energy is needed for factories and farms….
operating heavy-duty machines and production chains
How can distributing and producing electricity damage the environment?
Releasing energy from some stores causes pollution and harmful waste products. Burning fossil fuels releases carbon dioxide, adding to the greenhouse effect, and sulfur dioxide which causes acid rain.
What happened during the Industrial Revolution to do with transport?
During the
Industrial Revolution
, advances in automation and transport caused a significant increase in the amount of fossil fuels extracted and burnt.
What happened to electricity in the 20th century?
electricity became a convenient way of distributing energy that can be used for a wide range of devices and applications
List 5 examples of ways that energy can be used for a wide range of devices and applications….
lighting, heating, computing technologies and operating machinery.
Describe the demand for energy…
Demand for energy varies with the time of year and the time of day
Describe energy usage in the evenings…
During early evenings a lot of energy is needed for heating, lighting and cooking
Describe energy usage overnight…
overnight there is very little needed while people sleep.
Describe energy usage in the winter and compare it to the summer…..
During winter there is more heating and lighting required than in summertime.
Why is most of the electricity generated globally is still produced by fossil fuels?
1.the high power output fossil fuels give compared to other energy resources
2. the existing
infrastructure
for extracting, transporting and processing fossil fuels - this makes fossil fuels cheaper than setting up new alternatives
What is infrastructure?
The basic structures needed for an area to function, for example roads and communications.
What has caused the development of renewable energy sources?
The recognised impact on the environment of burning fossil fuels has caused science and society to develop the use of
renewable
energy resources and make machines more efficient.
What is a renewable energy source?
Energy sources that are replenished and not exhausted, eg solar power.
In some developed countries what energy source are a growing form of electricity generation?
Nuclear power stations
Why is nuclear power so popular in these developed countries?
Nuclear fuel can release large amounts of energy compared to fossil fuels and does not emit carbon dioxide. However, the radioactive waste that is produced is difficult to store and dispose of.
What are other factors that could influence governments’ decisions about the use of energy resources?
political and economic pressures.
What are Renewable resources replenished by?
Human action OR natural processes
Give an example of a human action to do with renewable energy….
trees cut down for biofuel are replaced by planting new trees
Give an example of a natural process to do with renewable energy….
water let through a dam for
hydroelectricity
is replaced through the
water cycle
What type of energy store are fossil fuels?
Chemical
Are fossil fuels renewable or non renewable sources?
Non renewable
What are fossil fuels used for?
Transport, heating, electricity generation
What is the power output of fossil fuel?
High
What impact do fossil fuels have on the environment?
Releases CO2 (causes global warming
What type of energy store is nuclear power?
Nuclear
Are nuclear fuels renewable or non renewable?
Non renewable
What are the uses for nuclear fuels?
Electricity generation
What is the power output of nuclear fuels?
Very high
What impact do nuclear fuels have on the environment?
Radioactive waste (needs to be disposed of safely)
What type of energy store is biofuel?
Chemical
Are biofuels renewable or non renewable?
Renewable
What are biofuels used for?
Transport, heating, electricity generation
What is the power output of biofuels?
Medium
What impact do biofuels have on the environment?
Carbon-neutral so low impact
What type of energy store is wind power?
Kinetic
Is wind power renewable or non renewable?
Renewable
What is wind power used for?
Electricity generation
What is the power output of wind power?
Very low
What impact does wind power have on the environment?
Take up large areas that could be used for farming, people say windmills spoil their view
What type of energy store is hydroelectricity?
Gravitational potential
Is hydroelectricity a renewable or a non renewable source?
Renewable
What is the power output of hydroelectricity?
Medium
What impact does hydroelectricity have on the environment?
Local habitats are affected by the large areas that need to be flooded to build dams
What type of energy store is geothermal?
Internal
Is geothermal energy renewable or non renewable?
Renewable
What is geothermal energy used for?
Electricity generation and heating
What is the power output of geothermal energy?
Medium
What impact does geothermal energy have on the environment?
Very low
What type of energy store are tides?
Kinetic
Are tides a form of renewable or a non renewable energy source?
Renewable
What are tides used for in terms of energy?
Electricity generation
What power output do tides have?
Potentially very high but hard to harness
What impact does tidal energy have on the environment?
Tidal barrages can block sewage which needs to go out to sea
What type of energy source is the sun?
Nuclear
Is the sun a renewable or a non renewable energy source?
Renewable
What uses does the sun have in terms of energy?
Electricity generation
How much power output does the sun have?
Potentially very high, but hard to harness
What impact does sun sourced energy have on the environment?
Very little
What type of energy store are water waves?
Kinetic
Is water wave energy renewable or non renewable?
Renewable
What is water wave energy used for?
Electricity generation
What is the power output of water wave energy?
Low
What impact does water wave energy have on the environment?
Very low
What 2 types of power stations provide much of the UKs electricity?
Power stations that uses fossil fuels or nuclear fuel
How long do nuclear and fossil fuel power stations run for?
They operate continuously
What happens when additional power is needed?
When additional power is needed, gas power stations are usually used because they will come on very quickly and start generating electricity almost immediately.
How expensive are nuclear power stations to run?
The fuel for nuclear power stations is relatively cheap, but the power stations themselves are expensive to build. It is also very expensive to dismantle, or
decommission
, old nuclear power stations at the end of their useful life
What does decommission mean?
To deactivate or remove in a safe manner.
How does the highly radioactive waste needs to be store?
The highly
radioactive
waste needs to be stored for millions of years before the natural
activity
will reduce to a safe level.
How reliable is wave power?
are reliable and predictable because of the Moon causing the tides and rainfall filling reservoirs. These two types can also be used to supply additional demand
Why are most renewable energy sources unreliable?
But many of the renewable sources are unreliable, including wind and solar energy, and cannot respond to increased demand - sunny and windy weather cannot be guaranteed.
What costs do renewable energy sources have?
Renewable resources have no fuel costs, but the equipment used is expensive to build.
