Energy Flashcards
What are the 8 energy stores?
Chemical (chemical bonds between atoms) Kinetic (a moving object) Gravitational (standing on top of a hill) Elastic (a stretched spring) Thermal (a warm object) Magnetic (magnets that attract or repel) Electrostatic (a charged balloon) Nuclear (inside the nuclear of an atom)
Energy is transferred from one energy store to another by what possible pathways?
By heating
By waves (e.g. light or sound waves)
By an electric current
By a force
What is the conservation of energy?
Energy cannot be created or destroyed. Energy is ALWAYS conserved- this means that energy can only be moved from one type of energy store to another type of energy store.
What is gravitational potential energy store?
Any time you lift an object you do some work, decreasing your own chemical store and increasing the GPE store of the object. The change in the GPE store of an object depends on:
The object’s mass
The planet’s gravitational field, g=10 on earth
The height the object is moved
Gravitational potential energy equation
GPE(Joules)= mass(kg) X gravitational field strength(N/kg) X height(m)
What is kinetic energy?
All objects that are moving have kinetic energy
Kinetic energy equation
KE(Joules)=1/2 X mass(kg) X speedsquared(m/s)
What is elastic potential energy?
An elastic object such as a spring or rubber band stores elastic potential energy(EPE)
Elastic potential energy equation
EPE(Joules)= 1/2 X spring constant(N/M) X extensionsquared(m)
What is energy dissipation?
Friction in machines always causes energy to be wasted- usually as heat. Wasted energy spreads out (dissipates) to the surrounding which becomes warmer.
What is efficiency?
Machines waste energy because of friction between their moving parts causing the object to heat up. Machines can be made more efficient by reducing the energy they waste. For example, putting oil in car engines reduces friction. The efficiency of a machine can be any number between 0 and 1
0= All energy is wasted
1= Zero energy is wasted
Efficiency equation
Efficiency= useful output energy(Joules) divided by total input energy(Joules)
What is power?
Power is how quickly you can transfer energy, or how quickly work is done. Power is measured in watts
Power equation
Power(watts)= energy transferred(Joules) divided by time taken(seconds)
What is conduction?
The process where vibrating particles transfer energy to neighbouring particles. Conduction passes on the heat energy through vibrations. It occurs mainly in solids because the particles are close together.
What does conduction need to occur?
Conduction needs particles to occur. It is a slow form of heat transfer. Energy gets passed down. Metals are good conductors because they also contain tiny particles called free electrons which are free to move and collide with other atoms, speeding up the heat transfer.
What is convection?
Convection is a heat transfer that takes place in liquids and gases. It is fast acting as the particles move with the energy.
How does convection work?
When a fluid (liquid or gas) is heated, its particles move further apart causing the fluid to expand and become less dense. Because the hot fluid is less dense compared to the fluid around it, it will begin to rise. When the hot fluid reaches the top of the container it cools, the particles move closer together causing it to become more dense so it falls. This circular movement is called a convection current.
What is infra-red radiation?
Infra-red is emitted from all objects. While IR radiation is a type of wave (just like light), we cannot see it as it sits beyond red in the visible spectrum. While we cannot ‘see’ IR, we can ‘feel’ it as heat energy. The hotter an object is, the more IR radiation it emits. IR can be detected using a thermometer or thermal camera. These pictures are called thermograms.
What surfaces are good absorbers of IR radiation?
Dark, Matt surfaces
What surfaces are good reflectors of IR radiation?
Light, shiny surfaces
What is specific heat capacity?
The amount of thermal energy needed to increase the temperature of 1kg of a substance by 1degreec
How much energy does 1kg of water need to become 1degreec hotter?
About 4,200 Joules
What materials with large SHC’s do we use in our central heating systems at home?
Water filled radiators
Oil filled radiators
Storage heaters (use bricks)
Does water have a high or low SHC?
Water has a very high SHC. It needs more energy to heat up, it stores more energy when hot, and it gives out more energy when it cools down.
What are thermos flasks designed to do?
Vacuum flasks are designed to keep hot things hot or cold things cold- this is done by reducing heat energy transfer
How does a thermos flask work?
Screw cap stops convection
Inside surface is silver (reflects IR radiation)
Vacuum (no particles therefore no convection)
Pad is a good insulator (no conduction)
Both conduction and convection require particles to happen. If you remove the particles then you prevent heat transfer by that method.
How do our homes lose heat?
Heat energy is also lost from houses by conduction (through the walls, floor, roof and windows), convection (cold drafts) and infra-red radiation (through the walls)
How do we keep our homes warm?
Double glazing (stops conduction)
Curtains & draft excluders (stops convection)
Loft insulation (stops convection)
Silver backed cavity wall insulation (stops conduction, convection and infra-red radiation).
What is the national grid?
A system of cables and transformers linking power stations to consumers.
What do step-up transformers do?
As electricity leaves the power station the voltage is increased (stepped-up) to 400,000volts using step-up transformers. This high voltage (and low current) reduces the amount of energy lost as heat in the power cables, making them more efficient.
If demand for electricity suddenly increases, this is called:
Pickup
What is supply and demand?
We find it very difficult to store electricity. We need to generate the electricity as we need to use it.
What is start-up time?
The time it takes from turning on a power station to it producing electricity.
Nuclear (days)-supplies the ‘base’ because it is left on all the time
Coal (hours)
Natural gas (minutes)
Hydroelectric (minutes)
What are the advantages of fossil fuels?
They can generate large amounts of electricity
They are cheap compared to other methods
They are a reliable source of energy production
What are the disadvantages of fossil fuels?
Pollution/global warming from producing CO2
Oil spills damage the environment
They are non-renewable
What is carbon capture?
A method to capture and store CO2 in deep underground geological formations. Therefore the CO2 won’t contribute to global warming
How does nuclear power work?
Inside a nuclear reactor, atoms of uranium or plutonium undergo a process called nuclear fission. This process releases a large amount of heat energy. This heat is used to turn water into steam, this steam then turns a turbine attached to a generator. This generates electricity.
Compare Nuclear and Fossil fuels
1kg of fuel will power a 100w light bulb for:
Nuclear: 1,000 years. Fossil fuels: 1,000 hours
Nuclear creates no greenhouse gases but creates nuclear waste. Fossil fuels are non-renewable
How do solar panels work?
Heat water using infra-red radiation from the sun. This water may then be used to heat buildings or provide domestic hot water
How do solar cells work?
Generate electricity directly from the sun’s radiation. Solar cells generate direct current when light energy is absorbed by them.
Reasons for and against wind turbines:
For: renewable and relies on wind which is very common in the Uk!
Against: not reliable, loud, kills birds, expensive
How does hydroelectricity work?
The water flowing from rivers has kinetic energy. We can turn this into electrical energy to use In our homes, we usually need to build a dam, and let the water flow through it gradually
Advantages and disadvantages of hydroelectricity:
Advantages:
Renewable, no pollution, we can store the water up high and then whenever we need the energy we can let the water out
Disadvantages:
Costs a lot of money to build a dam, the dam can ruin local environment because it changes where the water naturally flows, some animals and plants may die.
How does tidal power work?
The tides go in and out as they are pulled by the moon’s gravitational field, and we can capture energy from this massive movement of water (kinetic energy of water) with tidal power stations. A barriage is set across a Beach or river. When high tide comes in, water flows through a turbine to create electricity
Advantages and disadvantages of tidal power:
Advantages:
Running costs are very low- no fuel costs, just maintenance costs
Does not produce greenhouse gases or acid rain
Not expensive to maintain
Doesn’t need fuel
Disadvantages:
Very expensive to build
Create electricity only in time with the tides (not necessarily needed) the energy from them has to be stored for them to be efficient, fish may get killed
How does wave power work?
The waves arriving cause the water in the chamber to rise and fall, which means that air is forced in and out of the hole in the top of the chamber. We place a turbine in this hole, which is turned by the air rushing in and out.
Advantages and disadvantages of wave power:
Advantages:
The energy is free- no fuel or waste produced
Not expensive to operate and maintain
Can produce a great deal of energy
Disadvantages:
Depends on the waves- sometimes you’ll get loads of energy, sometimes almost nothing
Needs a suitable site where waves are consistently strong
Must be able to withstand very rough weather
How does geothermal work?
Possible in volcanic areas or where hot rocks lie quite near to the surface. The source of much of the energy is the slow decay of various radioactive elements, including uranium, deep inside the Earth. Can be used to generate electricity or to heat buildings directly
Advantages and disadvantages of geothermal:
Free energy, reliable, renewable, does not produce CO2, once water or steam is used it can be pumped back into the ground
Disadvantages:
Aren’t many suitable locations for power plants, cost of building a power plant is often high compared to the amount of energy it produces
How does Biomass work?
An organic material which can be burned to provide energy, e.g. heat, or electricity. After treatment with chemicals it can be used as a fuel in Diesel engines
Advantages and disadvantages of biomass:
Advantages:
Cheap and readily available, if replaced biomass can be a long-term sustainable energy source.
Disadvantages:
When burned it gives off atmospheric pollutants including greenhouse gases, biomass is only a renewable source of energy if the crops are replanted
