P1- Energy Flashcards
Outline the four types of energy transfer
Mechanical (by a force doing work), Electrically (work done by moving charges), Heating or Radiation (eg light or sound)
List the 8 types of Energy stores
Thermal, Kinetic, Gravitational P, Elastic P, Chemical, Magnetic, Electrostatic, Nuclear
Energy is never….?
Used up
Energy is not used up it is….?
Transferred between different objects and energy stores.
Where does energy go once it is transferred?
One of the objects energy stores
What is a system?
a single or group of objects
In a system, where can energy be transferred to?
into or away
between different objects in system or different energy stores
What is a closed system?
a system where neither matter nor energy can enter or leave
What is the net change in total energy of a system?
0
Define “work done”
Energy transferred
When can “work be done”
When current flows or by a force moving on an object
Equation for kinetic energy
Ek=1/2mv²
KE = 1/2 x mass x speed²
Joules = 1/2 x kg x m/s
When is energy transferred to and from the kinetic energy store?
To the store when an object speeds up
Away from it when the object slows down
What is kinetic energy?
Energy due to an object being in motion
When is energy transferred to gravitational potential energy stores?
If an object in a gravitational field is lifted, work is done and there is a transfer of energy to the store of the raised object.
When is more energy transferred to a GPE store?
If an object is lifted higher
Amount of energy in a kinetic store depends on….
Mass and speed
Amount of energy in a GPE store depends on….
Mass and height of the object
Strength of gravitational field
Equation for Gravitational Potential Energy
Ep = mgh
GPE = mass x GFS x height
Joules = kg x n/kg x m
Where is energy transferred when an object falls?
From its GPE store to its kinetic energy store
Where is energy from stretching or squashing transferred?
Elastic Potential Energy Store
Does the formula for EPE work after the limit of proportionality has been exceeded?
No
Define limit of proportionality
The point where the spring can no longer stretch and Hooke’s law is no longer true
Equation for EPE of a stretched spring
Ee = 1/2ke²
EPE=1/2xspring constantx extension²
Joules = 1/2 x n/m x m
What is Hooke’s law?
The strain in a solid is proportional to the applied stress within the elastic limit of that solid.
Define specific heat capacity?
The thermal energy required to raise the temperature of a substance
Equation that links energy transferred to specific heat capacity
△E = mc△θ
Change in thermal energy = mass x specific heat capacity X temperature change
Joules = kg X j/kg°C x°C
What is the conservation of energy principle
Energy can be transferred usefully, stored, dissipated but never created or destroyed
What happens to non useful energy transferred?
It is dissipated energy or wasted energy
Example of energy transfer (phone)
When using a phone, energy is transferred usefully from the chemical energy store of the battery in your phone.
Some energy is dissipated into the phones thermal energy store causing the phone to warm up.
Example of energy transfer (flasks and closed systems)
A cold spoon is dropped into an insulated flask of hot soup which is then sealed.
if the flask is a perfect thermal insulator the spoon and soup form a closed system.
Energy is transferred from the thermal energy store of the soup to the useless thermal energy store of the spoon. No energy has left the system.
What is power?
The rate of energy transfer or rate of doing work
What is power measured in?
Watts
One watt=
one joule of energy transferred per second
What is the equation for power?
P = E/t
P = W/t
Power = energy transferred or work done/time
Watts = joules/seconds
What is conduction and where does it occur?
The process where heat is transferred causing particles to vibrate more and collide with each other thus transferring energy to neighbouring particles. Occurs mainly in solids.
What is convection and where does it occur?
Where heat is transferred and the particles move faster and the space between particles increases. This causes the density of the heated region to decrease. The warmer and less dense region rises above denser cooler regions
so the particles move away from hotter to cooler regions creating a convection current if their is a constant heat source. Occurs only in liquids and gases.
What object creates convection currents?
Radiators
What are 2 ways of reducing unwanted energy transfer?
Lubrication and thermal insulation
What force does lubrication reduce?
Frictional forces
Friction causes energy to?
Be dissipated, usually to thermal store
How does lubrication reduce unwanted energy transfer?
Reduce friction between two objects surfaces .
What lubricants are usually used and why?
Liquids such as oil as they flow easily between objects and coat them.
What does insulation reduce and how?
Rate of energy transfer by heating
What is a way of heating (houses) to prevent energy loss and how does it work?
Use thick walls made of a material with a low thermal conductivity. Thicker walls and lower conductivity slow down the rate of transfer, meaning the building cools slower.
List 4 examples of thermal insulation in houses
Cavity walls
Loft insulation
Double glazed windows
Draught excluders
What is a cavity wall?
Used in some houses, made up of an inner and outer wall with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls.
What is cavity wall insulation?
Where the cavity wall air gap is filled with a foam to reduce energy transfer by convection in the wall cavity.
What is loft insulation?
Insulation on ceiling and floor that reduces convection currents being created in lofts.
What are double glazed windows?
Air gap between two sheets of glass to prevent energy transfer by conduction through the windows.
What are draught excluders?
Sealants or objects around doors and windows to reduce energy transfer by convection.
What makes something efficient?
Wasting little energy
Efficiency equation
Useful output energy transfer/total input energy transfer
Useful power output/total power output
Are any devices 100% efficient?
Yes but only electric heaters as all the energy in the electrostatic energy store is transferred to a useful thermal energy store
Name the 2 types of non renewable energy resources
Fossil fuels and nuclear fuel
List the 3 main fossil fuels
Coal
Oil
Gas
List the 2 nuclear fuels
Uranium
Plutonium
List 2 advantages and 2 disadvantage of non renewable fuels
- They will all run out
- They do significant damage to the environment
- They provide most of our energy
- They produce more energy and are cost efficient
List 7 renewable energy resources
Solar
Wind
Water waves
Hydro electricity
Bio fuel
Tides
Geothermal
List 2 advantages and 2 disadvantages of renewable energy
- They will never run out
- They do less damage to the environment
- They dont provide as much energy so not cost efficient
- They are unreliable due to weather dependency
What is wind power?
Putting up lots of wind turbines in exposed areas like moors or round coasts.
How do wind turbines work?
They have a generator inside, the blades turn the generator and produce electricity.
Positives and negatives of wind turbines are….
- No pollution (except during manufacturing)
- Spoil the view
- Very noisy
- Reliant on wind
- Initial costs are high
- Low running cost and no fuel costs
- No permanent damage to the area
How do solar cells work?
Generate electric currents directly from sunlight.
What are solar cells used for?
- Best option for charging small batteries
- Used in remote hot areas for signs and satellites
Positives and negatives of solar cells are….
- There is no pollution
- They use a lot of energy to manufacture
- Very reliable in sunny countries but only during the day
- Cant increase the power output when there is extra demand
- High initial cost
- Nearly free once running
- Usually used for small scale generation
How does geothermal power work?
Energy from heating rocks, possible in volcanic areas where hot rocks lie near to the surface. Source of energy is slow decay of radioactive elements such as uranium deep inside the earth.
Positives and negatives of geothermal energy are….
- Free energy
- Very reliable
- Little damage to environment
- Not many suitable places for power plants
- Power plants are high cost to build compared to the energy they produce
What is geothermal energy used for?
Generating electricity or directly heating buildings
How does hydroelectricity work?
Uses falling water and requires the flooding of a valley by building a big dam. Water is allowed out through turbines.
Positives and negatives of hydroelectricity are….
- No pollution
- Big impact on environment as flooding causes loss of habitat, rotting vegetation releasing CO2, bad views
- Immediate response and reliable in UK
- High initial cost but low running costs
What is hydro electricity used for?
Small scale energy production in remote areas
How does wave power work?
Uses lots of wave powered turbines around the coast, connected to generators like wind turbines.
Positives and negatives of wave power….
- No pollution
- Disturbing the seabed and marine animals
- Spoils the view
- Hazard to boats
- Unreliable as waves die out when wind drops
- High initial cost but low running cost
What is wave power used for?
Not likely to be used on large scale but useful on small islands.
How do tidal barrages work?
Big dams built across river estuaries, with turbines in them, as the tide comes in it fills up the estuary and the water is then allowed out through turbines at a controlled speed. Tides are produced by the gravitational pull of the Sun and Moon.
Positives and negatives of tidal barrages….
- No pollution
- Prevents free access by boats
- Spoils view
- Alters habitat of wildlife
- Tides happen twice a day without fail, near predicted height, reliable
- Height is variable so lower (neap) tides provide less energy than bigger (spring) tides
- Dont work 4 times a day when water level is same on both sides
- High initial costs but no fuel costs and minimal running costs
- Potential to generate lots of energy
How do biofuels work?
Created from ant products or animal faeces. They can be solid, liquid or gas and are burnt to produce energy
Positives and negatives of biofuels….
- Supposedly carbon neutral but only technically true if you grow plants at the rate you burn them
- Fairly reliable as crops are quick to grow
- Produced and stored to be used in case of immediate energy demand
- High cost to refine fuels
- Lots of space needed cause loss of habitat and deforestation
- Burning of vegetation increases CO2 and methane emissions
What are biofuels used for?
To produce electricity and run cars, in the same way as fossil fuels
Why are non renewables reliable/unreliable?
There is enough of them to meet current demand, they are extracted quick enough to always be in stock, cost effective.
They are slowly running out due to not being reusable.
What problems do non renewables create for the environment?
Release large amounts of CO2 adding the greenhouse effect and contributing to global warming.
Coal and oil release sulfur dioxide which causes acid rain.
Mining ruins landscape.
Oil spills affect sea animals.
Nuclear is extremely dangerous, disasters such as Fukushima in Japan
What can nuclear radiation cause to happen to humans?
Cancer
How are we dependent on fossil fuels?
Electricity use is increasing and they are cheapest, fastest, most effective option we have.
