Energy Flashcards
State the nine different forms of energy
Kinetic (Ke) - movement energy
Gravitational Potential Energy (gpe) - when an object is lifted
Elastic Potential Energy (epe) - when an object is stretched or compressed
Chemical - stored in chemical bonds (fuels like food)
Heat (thermal) - often wasted energy
Sound - often wasted energy
Light - often wasted energy
Electrical
Nuclear- stored in nuclear bonds and released in atomic bombs/nuclear power stations (from the nucleus of an atom)
What is an easy way of remebring the nine forms of energy?
Every (elastic)
Kid (kinetic)
Loves (light)
Not (nuclear)
Hates (heat)
G (gravitational)
C (chemical)
S (sound)
E (elastic)
State the law of the conservation of energy
‘Energy cannot be created or detroyed but can be converted from one form into another.’
Can the amount of energy in the universe change? Why?
no because of the principle of the conservation of energy (it cannot be created or destroyed so there cannot be more or less)
What is energy?
energy is the ability to do work on objects and it converts from one form to another
What is work?
work is done when force is applied to an object and the object is moved through a distance
What is the equation for work?
work = force x distance moved in the direction of the force
measurements - Joules (J) = Newtons (N) x Metres (m)
w= f x d
What is the equation for GPE?
GPE= mass x gravity x height
measurments- Joules (J) = kg x N/kg x m
gpe = mgh
What is the equation for kinetic energy?
kinetic energy= 1/2 x mass x velocity2
measuremnts - Joules (J) = kg x v in m/s
Ek = 1/2 mv2 (notice only v is squared)
What is power?
power is the rate of doing work
rate means per time/per unit time
What is the equation for power?
power = work ÷ time
p= w÷t
What is power measured in?
power is measured in Watts
1W= 1 J/s
1KW = 1000W
1MW = 1000,000 W
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Calculate the increase in GPE for the girl in going between G and A floor
GPE= mgh
=65 x 10 x(6 x 1)
=3900 J
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Calculate the total increase in her GPE from G to D floor
GPE= mgh
= 65 x 10 x (6 x 4)
= 15600J
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Explain why she feels tired
she has done work by walking
she has converted chemical energy into gravitational, kinetic and thermal energy
A 200g mass is lifted 5.0m off the ground. Calculate the work done in lifting it
GPE= mgh
0.2 (remember to convert 200g into kg) x 10 x 5
=10J
A 900kg car is moving at 5 m.s. how much kinetic energy does it have?
Ek= 1/2 mv2
=1/2 x 900 x (5)2
=450x25
=11250 J
A 90kg runner is moving at a constant velocity of 12 m/s. Calculate the kinetic energy
Ek= 1/2 x 90 x (12)2
=6480J
A 1000kg car is travelling at 15m/s on the motorway. Calculate the work done (change in energy) when it accelerates to 18 m/s
Ek= 1/2 x 1000 x (182-152) [You have to take the original velocity away from the new velocity]
= 49500J
Rearrange the kinetic energy equation so that velocity is the subject
Ek=1/2 x m x v2
Ek x 2 = m x v2
Ek x 2 ÷ m = v2
v2 = 2Ek/m
v = √ 2Ek/m
A 700kg car has 12000J of kinetic energy. Calculate its velocity
v = √ 2Ek/m
v = √ 2x12000/700
=5.86 m/s (2.dp)
What is the efficiency and its equation?
how much useful energy is produced from the total energy put into the machine
effeciency = total useful output/total input x 100
What is a sankey diagram?
it shows how well a machine uses energy
shows efficiency or inefficiency of something
How do you draw a Sankey Diagram?
the thicker the arrow, the more energy it represents
useful energy is shown going left or right
wasted energy is shown going upwards or downwards
the length of the arrows doesn’t matter
if on graph paper or specified, every square and placing matters (the starting of the output and the calculations of the thickness of the arrow)
A car increases its kinetic energy from 120,000J to 150,000J in 15 seconds. What work is done by the car in increasing its kinetic energy?
30,000J
A car increases its kinetic energy from 120,000J to 150,000J in 15 seconds. What is the power output of the car?
=30,000J ÷ 15 secs
=2,000W (2KW)
A car increases itsr kinetic energy from 120,000J to 150,000J in 15 seconds. The engine is rated at 3.5KW. How efficient it it?
efficiency =output/input x 100
=(30,000/15) / 3500 x 100
=2000/3500 x 100
=57%
When a ball is held above the ground what form of energy does it have?
gravitational potential energy (gpe)
What form of energy does a falling ball have half way to the ground?
1/2 gpe
1/2 kinetic energy
What form of energy does a ball have as it is bouncing?
elastic potential energy (epe)
heat (thermal) energy
sound energy
What happens in terms of energy as a ball falls?
gpe is converted into kinetic energy
What happens in terms of energy as a ball is during the bounce stage?
kinetic energy is converted into elastic potential energy, thermal energy and sound energy
What happens in terms of energy as a ball bounces up to its highest point?
elastic potential energy is converted into kinetic energy which is converted into gravitational potential energy
A scientist observes an experiment of a falling apple. He notices that the actual velocity of the apple is much lower than the value calculated. Explain what could cause this observation
he didn’t take into consideration air resistance
air resistance will do work on the apple as it falls
converting (or transferring) some of the oringinal gpe into thermal energy and sound energy
An observer says that the man must be cheating because he starts off at 4m and ends up 6m off the ground. He says that he is breaking the law of the conservation of energy. He also says that after reach 6m of the ground (at D) he landed and only reached the top of the half pipe at the other side (at A). He then says that he must of cheated as he should have reached 6m off the ground at the other side too.
Evaluate this comment
(do not need to mention all of these)
mention of 3000J of energy at the start
needs more energy to reach D
extra 1500J needed
skateboarder must add extra 1500J
skateboarder does 1500J of the work
w=fd (by the skateboarder)
mention that energy must be conserved
mention of friction
mention dissipated energy into the atmosphere
mention would need to push/do workto reach C to overcome friction/ air resistance
not cheating (if liknked to scientific reason)
What is the difference between renewable and non-renewable fuels?
renewable = replenishes itself so will never run out
non-renewable = used faster than made so will one day run out
Give some examples for renewable and non-renewable fuels?
renewable = solar, tidal, wave, wind, hydrolic, wood, geothermal
non-renewable = oil, coal, natural gas, nuclear
What are the names of fossil fuels?
coal, oil, natural gas (non-renewable)
What is the greenhouse effect?
caused by greenhouses gases (CO2 methane) and cause global waming
- absorbed radiation - the Earth absorbs radiation from the sun
- Reflected radiation - greenhouse gases absorb some outgoing radiation
- Greenhouse gases - greenhouse gases emit absorbed raidation - this warms the earth and its atmosphere
What are some disadvantages of burning fossil fuels to generate electricity?
All fossil fuels release carbon dioxide (CO2) into the atmosphere when burned in power stations. All this CO2 contributes to global warming and climate change
Burning coal and oil also releases sulphur dioxide (SO2), which causes acid rain. Acid rain can harm trees and soils and can have a huge impact on wildlife and the environment
They will eventually run out
What is meant by ‘clean’ fuel?
doesn’thurt the planet, global warming
they don’t produce pollution or greenhouse gases
What are the advantages of using non-renewable energy sources??
Burning folssil fuels releases a lot of energy, relatively cheapily
Energy from fossil fuels doesn’t rely on weather, like a lot of renewable energy, so it’s a reliable energy source
We have lots of fossil fuel power stations already, so we don’t need to spend money on new technology to use them
What are the disadvantages of using Solar Power, Wind Power, Tidal Power, Wave Power, Geothermal, Wood to generate electricity?
wood takes a lot of space
geothermic is expensive in the UK
not constant or necassarily quick
effects wildlife and areas such as flooding and birds
Why is geothermal energy expensive and not a good source of energy in the UK?
you would have to dig down very deep which is very expensive and time consuming and you would only produce a small amount of energy
Why is solar powerful ineffective in the UK?
there is not enough sunlight to generate enough power
Talk about the fact that some power stations respond quickly to changes in demand?
power stations = slow
hydroelectric power = fast
responses differ
Why are nuclear power stations expensive to decommision?
you have to dispose of the waste
they only last 30 years
nuclear waste must be disposed off carefully
land has to be un-radioactive after
burning coal takes a while
What are the cost considerations in the choice of power stations?
different expenses depening on size - they have differnet energy outlets
decommisioning and removing nuclear waste is very expensive
Why does demand for electricity change through the day and seasons?
winter needs more electricity - heat especially
sleeping = less electricity
celebrations or events e.g. the world cup
What causes predictable changes in demand on a day to day and season to season basis?
rush hour
morning kettle
sleep vs daytime
tv
what is the energy transfer for an electric kettle boiling water
electrical energy to thermal energy
what is the energy transfer for coal burning in an open fire
chemical energy to light energy
what is the energy transfer for a weight as it is falling through the air
kinetic energy to gravitational potential energy
it’s a typical english winter everning; dark, wet but calm
the demand for electricity is also typical for this time of year and is being met by all fossil fuel power stations working at maximum output along with half the nuclear power stations
an event occurs that suddenly causes demand throughout the UK to increase by 50%
use your knowledge of start up times and reliability of energy sources to say whether or not you would use these energy resources and why:
the remaining nuclear power stations
wind farms across the country
solar power across the country
hydroelectric plants in Scotland
the remaining nuclear power stations: no - slow start up, couldn’t use staright away
wind farms across the country: no - the weather is calm (no wind)
solar power across the country: no - it is dark (nighttime) so there is no sun
hydroelectric plants in Scotland: yes - very quick and reliable, it is a wet day meaning it rained all day
less time = … work = … powerful
less time = less work = less powerful
A light bulb changes … energy into useful … energy
A light bulb changes electric energy into useful light energy
A petrol engine changes … energy into useful … energy
A petrol engine changes chemical energy into useful kinetic energy
Most of the energy lost is as … energy
Most of the energy lost is as thermal energy
A human muscle changes … into useful … energy
A human muscle changes chemical into useful kinetic energy
convert 1kJ into J
1kJ = 1000J
Which energy source only works in volcanic regions?
geothermal
Which energy source is usually situated on a hill?
wind
Which fuel produces the most sulphur dioxide, a greenhouse gas?
coal
A microphone changes … into useful … energy
A microphone changes sound into useful electric energy
What happens to wasted energy?
wasted energy is dissipated into the suroundings
Energy is …
Energy is the ability to do work
What are two examples of light energy?
the Sun
light bulbs
What is an example of sound energy?
loudspeakers
What are three examples of elastic potential energy?
springs
elastic
rubber bands
What are three examples of chemical energy?
foods
fuels
batteries
Energy is only useful when …
Energy is only useful when it is transferred from one form to another
A television turns … energy into … and … energy
A television turns electrical energy into light and sound energy
Toy car batteries turn … energy into … energy into … , … , … and … energy
Toy car batteries turn chemical energy into electrical energy into kinetic , heat , sound and light energy
Battery chargers convert … energy into … energy
Battery chargers convert electrical energy into chemicalenergy
Electrical devices convert … energy into … , … and … energy
Electrical devices convert electrical energy into sound , light and heat energy
Batteries convert … energy into … energy to run electrical devices
Batteries convert chemical energy into electrical energy to run electrical devices
Gravitation and elastic potential energy always get converted into … energy first
Gravitation and elastic potential energy always get converted into kinetic energy first
A crane converts … energy into … energy into … energy
A crane converts chemical energy into kinetic energy into gravitational potential energy
A falling object converts … energy into … energy
A falling object converts gravitational potential energy into kinetic energy
An archer converts … energy into … energy
An archer/bow converts chemical energy into elastic potential energy
A bow/arrow converts … energy into … energy
A bow/arrow converts elastic potential energy into kinetic energy
A powerful machine is one which …
A powerful machine is one which transfers a lot of energy in a short space of time
What are the unites of work?
Joules (J)
What are the units of energy?
Joules (J)
What are the units of power?
Watts (W)
What does a detailed sanky diagram look like (i.e. one on a graph)?
From where is most of our energy provided?
fossil fuels (non-renewable energy resources)
What is energy conservation?
using fewer resources because of the damage they do and because they might run out
Most power stations use … to drive a turnbine. How does this work?
chemical energy, in the form of fuel, is fed into a boiler
Heat energy released is used to heat water to create steam which turns a turbine (kinetic energy)
The kinetic energy turns the generator which converts the kinetic energy into electrical energy which flows to a grid
chemical energy → heat energy → kinetic energy → electrical energy
How does a nuclear reactor work?
nuclear fission, e.g. of uranium, priduces heat to make steam to drink turbines, rather than burning
nuclear energy → heat energy → kinetic energy → electrical energy
Nuclear reactors are cheap/expensive to build and mantain
They take a shorter/longer time to start up than fossil fuel ones
Nuclear reactors are expensive to build and mantain
They take a longer time to start up than fossil fuel ones
What are the environmental impacts of using a nuclear reactor?
processing uranium before you use it causes pollution
there is always a risk of leaks of radioactive material, or even a major catastrophe like at Chernobyl
you always get radioactive waste
What are the advantages to nuclear power?
it doesn’t produce any of the greenhouse hases which contribute to global warming
there’s still plenty of uranium left in the ground (although it can take a lot of money and energy to make it suitable for use in a reactor)
How do wind turnbines work?
Wind power involves putting lots of wind turbines up in exposed places - like on moors, around the coast or out at sea
Wind turbines convert kinetic energy of moving air into electrical enrgy. Wind turns the bldes, which turn the generator inside it
What are the advantages to wind turbines?
they are quite cheap to run - they’re very tough and reliable and the wind is free
wind power doesn’t produce any polluting waste
it is renewable - wind is never going to run out
What are the disadvantages to wind turbines?
they spoil the view
you need 1500 wind turbines to replace one coal-fired power station and 1500 of them cover a lot of ground which has a big effect on the scenery - annoying for the people who live nearby
sometimes the wind isn’t strong enough to generate any power
it is impossible to increase power supply when there’s extra demand
although the wind is free, its expensive to set up a wind farm, especially out at seas
Where is geothermal energy possib;e? What is the source of much of the heat?
geothermal energy is only possible in certain places where hot rocks lie quite near to the surface
the source of much of the heat is the slow decay of various radioactive elements. including uranium deep inside the Earth
How does geothermal energy work?
water is pumped in pipes down to the hot rocks and forced back up due to pressure to turn a turbine which drives a generaor
heat energy → kinetic energy → electrical energy
in some places, geothermal energy is used to heat building directly
What is are the advantages of geothermal energy?
it is free
it is a renewable energy resource
there are no real environmental problems
What is are the disadvantages of geothermal energy?
the cost of driviling down several kilometres
the cost of building a power plant is often high compares to the amount of energy we can get out of it
there are few places where geothermal energy seems to be an economic option
What do solar cells do?
solar cells (photocells) transform light energy from the Sun directly into electrical energy
they generate direct current (d.c.) - the same as a battery
What are the advantages of solar cells?
the Sun provides a renewable energy source - it won’t run out (not for 5 billion years)
solar cells are expensive initially, but after that the energy is free and the running costas are almost nil
there’s no pollution (although they use a fair bit of energy to manufacture in the first place)
When are solar cells used?
solar cells are used to generate electricity on a relatively small scale, e.g. powering individual homes
they are the best way to power calculators or watches that don’t use much energy
Where are solar cells used?
solar cells are used in remote places where there’s not much choice (e.g. deserts) and in satellites
Are solar cells connected to the National Grid? Why?
It’s often not practical or too expensive to connect solar cells to the National Grid - the cost of connectng them can be enormous compared with the value of electricity generated
When do solar cells generate electricity? What can be done to store energy?
solar cells can only generate enough electricity to be useful if they have enough sunlight - which can be a problem at night (and in the winter in some places)
the cells can be ilnked to rechargeable batteries to create a system that can store energy during the day for use at night
What are solar panels? How do they work?
solar panels are more simple than solar cells - they’re basically just black water pipes inside a glass box
the glass lets heat and light from the Sun in, which is then absorbed by the black pipes and heats up the water
What are the advantages and disadvantages of solar panels? When are they used?
they cost money to set up, but are renewable and free after that
they’re only used for small-scale energy production
How does wave power work?
one way of harvesting wave power is with lots of small wave converters located around the coast
as waves come in to the shore they provide and up and down motion which can be used to drive a generator
the kinetic energy of the waves is converted into electrical energy
What are the advantages of wave power?
there is no pollution
it is renewable
the initial costs are high but there are no duel costs and minimal running costs
What are the disadvantages of wave power?
wave converters spoil the view
wave converters are hazards to boats
it is fairly unreliable, since waves tend to die out when the wind drops
On what scale is wave energy used?
wave energy is unlikely to provide energy on a large scale but it can be very useful on small islands
What are tidal barrages and how do they work?
tidal barrages are big dams built across river estuaries with turbines in them
as the time comes in it fills up the estuary to a height of several metres
this water can then be allowed out through turbines at a controlled speed
it also drives the turbine on the way
the kinetic energy of the water is converted into electrical energy by the turbines and a generator
What are the advantages to tidal power?
there is no pollution
it’s renewable
tides are pretty reliable, but the height of the tide is variable so lower tides will provide less energy than higher ones
initial costs are moderately high, but there’s no fuel costs and minimal running costs
What are the disadvantages to tidal power?
tidal barrages prevent free access by boats
tidal barrages spoil the view
tidal barrages alter the habitat of the wildlife
How does hydroelectric power work?
hydroelectric power often requires the flooding of a valley by building a dam
rainwater is caught and allowed out through turbines, converting the gravitational potential energy of the water into kinetic energy as it falls, which is then converted into electrical energy by the generator
gravitational potential energy → kinetic energy → electrical energy
What are the advantages to hydroelectric power?
it’s a renewable resource
it can respond immediately to increase demand - if more energy is needed than the National Grid can supply, the water is released
there is no problem of reliability except in times of drought
initial costs are high, but there’s no fuel and low running costs
What are the disadvantages to hydroelectric power?
There is no pollution (as such), but there’s a big impact on the environment due to flooding the valley (rotting vegetation releases methane and CO2) and possible loss of haitat for some species - location in remote valleys can avoid some of these problems
The reservoirs can also look very unsightly when they dry up - location in remote valleys can avoid some of these problems
Pumped storage gives extra supply just when it’s needed
Why is is it needed? How does this work?
Most large power station have huge boilers which have to be kept running all night even though demand is very low. This means a surplus of electricity at night - and its very difficult to find a way to strore this spare energy of electricity at night. Pumped strogae is one of the best solutions
In pumped storage, ‘spare’ night-time electricity is used to pump water up to a higher reservoir
This can then be released quickly during periods of peak demand such as at teatime each evening, to supplement the steady delivery from the bigger power stations
It is simply a way of storing energy which has already been generated
