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30/04/2015
Living for the Future
W Richards
The Weald School
(OCR Gateway Additional Science)
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P2a Collecting Energy from the Sun
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Solar Panels and Thermal Towers
What are the advantages and
disadvantages of solar power?
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Using Solar Energy in remote places
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Solar Energy Solar panels – convert sunlight directly into ______. Sunlight knocks ______ loose from the crystal structure and the loose electrons form a DC electric ______. The amount of power depends on the ___ of the panel and the light ______ and the distance to the ____.
Words – current, electricity, electrons, sun, area, intensity
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Other ways to use solar energy
Heating for homes – these pipes carry water that absorbs heat energy and transfers it to the house.
Using curved mirrors and solar panels – these curved mirrors focus light onto a chosen point and efficient ones can track the sun across the sky
Wind power – heat from the sun causes convection currents which then form wind.
What are the advantages and disadvantages of wind power?
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Passive solar heating “Passive solar heating” is the idea of using solar power to heat homes. Here’s how they work:
1) Glass is transparent to the sun’s radiation
2) The “thermal mass” next to the glass absorbs the sun’s heat energy
3) The surface then emits radiation of longer wavelength
4) The glass helps reflect the infra red back inside the house
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P2b Generating Electricity
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DC stands for “Direct Current” – the current only flows in one direction. Batteries supply DC.
AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz). Household electricity is AC
1/50th s
230V
V
V
Time
T
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Generating Electricity
The direction of the generated current is reversed if…
1) The magnet is moved in the opposite direction
2) The other pole is inserted first
The size of the generated current can be increased by:
1) Increasing the speed of movement
2) Increasing the magnet strength
3) Increasing the number of turns on the coil
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Induced current can be increased in 4 ways:
1) Increasing the speed of movement
2) Increasing the magnetic field strength
3) Increasing the number of turns on the coil
4) Increasing the area of the coil
N S N S
Current
Time
30/04/2015 Using non-renewable fuels in power stations
1) A fossil fuel is burned in the boiler
2) Water turns to steam and the steam drives a turbine
3) The turbine turns a generator
4) The output of the generator is connected to a transformer
5) The steam is cooled down in a cooling tower and the electricity is sent into the National Grid
30/04/2015 Efficiency Efficiency is a measure of how much USEFUL energy you get out of an object from the energy you put INTO it.
For example, consider a TV:
Electrical Energy (200J) Sound (40J)
Efficiency = Useful energy out
Energy in x100%
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Some examples of efficiency… 1) 5000J of electrical energy are put into a motor. The
motor converts this into 100J of movement energy. How efficient is it?
2) A laptop can convert 400J of electrical energy into 240J of light and sound. What is its efficiency? Where does the rest of the energy go?
3) A power station is 50% efficient. If it delivers 20,000J of electrical energy how much chemical energy was put into it?
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Efficiency of Power Stations
100J Boiler 85J Turbine 35J
Generator 30J
Heat
Heat Kinetic
Heat Heat
Electrical
What is the efficiency at each stage of this power station?
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P2c Global Warming
The following two graphs are taken from Wikipedia. What do they imply?
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The Greenhouse Effect We get heat from the sun:
Here’s how the greenhouse effect works:
1) Our atmosphere absorbs a lot of infra red ________ from the sun
2) Short wavelength EM radiation from the sun is absorbed by the _______ and heats it up
3) The Earth re-radiates heat as _______ wavelength EM radiation (i.e. _______ _____)
4) Greenhouse gases such as _____, carbon dioxide and water vapour absorb some of this infra red and re-radiate it back to the Earth causing it to ______ up.
Words – longer, radiation, Earth, warm, infra red, atmosphere
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The Changing Greenhouse Effect The Greenhouse Effect has been around for millions of years but scientists are concerned that it has been increasing in recent decades. How have the following things affected this?
Deforestation Factory pollution Volcanoes
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Differing views on Global Warming The following data shows global warming figures and projections from different research centres. What do you notice?
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P2d Fuels for Power
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Fuels A “fuel” is something that can be burned to release heat and light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.
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Nuclear power stations These work in a similar way to normal power stations:
The main difference is that the nuclear fuel (uranium) is NOT burnt – it is used to boil water in a “heat exchanger”
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Biomass “Biomass” is a term used to describe anything that can be grown or biologically made and then burned as a fuel:
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Non-renewable energy sources
Coal, oil, gas and nuclear
Advantages Disadvantages
Cheap fuel costs
Short start-up time for gas and oil
Good for “basic demand”
Fuel will run out
Costs a lot of money to
decommission a nuclear plant
Pollution – CO2 leads to global warming and SO2
leads to acid rain
Reliable
Nuclear produces little pollution
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Renewable energy sources summary
Wind, tidal, hydroelectric and solar
Advantages Disadvantages
Zero fuel costs
Hydroelectric is good for a
“sudden” demand
Don’t produce pollution
Ugly and the energy produced by them is very
“dilute”
Unreliable (except for
hydroelectric)
Expensive to build
Solar is good for remote locations (e.g. satellites)
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Energy and Power The POWER RATING of an appliance is simply how much energy it uses every second.
In other words, 1 Watt = 1 Joule per second
E
T P
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)
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Some example questions 1) What is the power rating of a light bulb that transfers
120 joules of energy in 2 seconds?
2) What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?
3) Rob runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?
4) How much energy does a 150W light bulb transfer in a) one second, b) one minute?
5) Jonny’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a 50 minute physics lesson?
6) Lloyd’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?
60W
2KW
150J, 9KJ
120KJ
630MJ
0.2MW
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The Cost of Electricity Electricity is measured in units called “kilowatt hours” (kWh). For example…
A 3kW fire left on for 1 hour uses 3kWh of energy
A 1kW toaster left on for 2 hours uses 2kWh
A 0.5kW hoover left on for 4 hours uses __kWh
A 200W TV left on for 5 hours uses __kWh
A 2kW kettle left on for 15 minutes uses __kWh
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The Cost of Electricity To work out how much a device costs we do the following:
Cost of electricity = Power (kW) x time (h) x cost per kWh (p)
For example, if electricity costs 12p per unit calculate the cost of the following…
1) A 2kW fire left on for 3 hours
2) A 0.2kW TV left on for 5 hours
3) A 0.1kW light bulb left on for 10 hours
4) A 0.5kW hoover left on for 1 hour
72p
12p
12p
6p
Electricity is cheaper at night time (around 5p per unit) – how much would these devices cost at night time?
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Power Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by: P
I V Power = voltage x current
in W in V in A
We can use this equation to analyse power stations:
1) A transformer gives out 10A at a voltage of 50V. What is its power output?
2) An electric fire has a power rating of 2KW. If it runs on a voltage of 230V what is the current?
3) Electricity is transmitted along some lines in the National Grid at 400KV. If the current is 1KA what would be the power through the wire?
500W
8.7A
400MW
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If electricity companies transmitted electricity at 240 volts through overhead power lines there would be too much ______ loss by the time electricity reaches our homes. This is because the current is ___. To overcome this they use devices called transformers to “step up” the voltage onto the power lines. They then “____ ____” the voltage at the end of the power lines before it reaches our homes. This way the voltage is _____ and the current and power loss are both ____.
Words – step down, high, power, low, high
Power station Step up
transformer Step down
transformer Homes
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P2e Nuclear Radiations
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The structure of the atom
ELECTRON – negative, mass nearly nothing
PROTON – positive, same
mass as neutron (“1”)
NEUTRON – neutral, same
mass as proton (“1”)
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Introduction to Radioactivity Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation:
Radiation
The nucleus is more stable after emitting some radiation – this is called “radioactive decay”.
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Background Radiation
Radon gas
Food
Cosmic rays
Gamma rays
Medical
Nuclear power
13% are man-made
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Blocking Radiation Each type of radiation can be blocked by different materials:
Sheet of paper
Few mm of aluminium
Few cm of lead
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Ionisation Radiation is dangerous because it “ionises” atoms – in other words, it turns them into positive ions by “knocking off” electrons or negative ions by gaining electrons:
Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.
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Uses of Alpha Radiation
Smoke detectors
Alarm
+ve electrode
-ve electrode
Alpha emitter
Ionised air particles If smoke enters here a current no longer flows
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Uses of Beta Radiation
Rollers
Beta emitter
Beta detector
Paper
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Uses of Gamma Radiation
Sterilising medical instruments
Gamma rays can be used to kill and sterilise germs without the need for heating.
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Other uses of radioactivity 1) Medical uses – gamma rays can be used to destroy cancerous cells
2) Tracers – a tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe:
Gamma source
Tracers can also be used to develop better plant fertilisers and in medicine to detect tumours:
The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected.
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Handling Radioactive Materials
Safety measures:
1) Keep your distance
2) Minimise exposure time
3) Protective clothing
4) Careful labelling
Plutonium is a waste product from nuclear power stations and can be used to make nuclear bombs. It remains radioactive for a long time and can be a terrorist risk.
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Disposing of radioactive waste
High level waste is immobilised by mixing with ____ making ingredients, melting and pouring the glass into steel containers.
Intermediate waste is set in cement in _____ drums.
The key to dealing with radioactive waste is to IMMOBILISE it. There are a number of ways of doing this depending on how __________ the waste is:
The containers are then kept in stores, often _________.
Words – glass, steel, underground, radioactive
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P2f Exploring our Solar System
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The Solar System summarised What makes up our solar system? Complete the following mind map with what you now about each object:
The solar system
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Mercury
Mars
Jupiter
Saturn
Neptune
Uranus
Venus Earth
As well as the eight planets, the solar system is also made up of asteroids, dwarf planets, comets and moons
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Distances in space
The Sun, our closest star, is 1.6x10-5 light years away from us.
The Andromeda Galaxy (our closest galaxy) – approximately 2.5 million light years away
The next closest star, Proxima Centauri (4.2 light years away)
The centre of our galaxy, the Milky Way, is around 26,000 light years away.
Definition – a “light year” is the distance covered by light every year
30/04/2015 Solar systems, galaxies and the Universe
OUR SUN (100 times wider and 4.6 billion years old), which is small compared to…
THE MILKY WAY, which contains at least 200 billion stars and is 100,000 light years across, which is small compared to…
Our planet (around 13,000km diameter and 4500 million years old) is pretty small compared to...
THE UNIVERSE, which contains billions of galaxies and is 14,000 million years old.
30/04/2015 How our Earth and the Sun compare to others…
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Elliptical Orbits
Ellipse
30/04/2015 The Earth is kept in orbit by 2 things…
Gravity
…and by the fact that it is moving at a high velocity
This is called a “centripetal force”
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Searching for Aliens Humans have been searching for me for over 50 years. Here are some of the methods they use:
SETI – The Search for Extra Terrestrial Intelligence
Since 1960 a group of astronomers have collectively been sending out EM signals hoping that someone will send one back!
Space probes
The Voyager 1 probe, still in operation after over 33 years and still sending signals back to Earth.
Soil samples
Soil samples from the moon and, in recent years, from Mars have been sampled.
What are the advantages and
disadvantages of each of these methods?
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Space Travel
Manned space travel
Unmanned space travel
Advantages Disadvantages
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P2g Threats to the Earth
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The moon The moon may be the remians of a very old planet. The Earth-Moon system
was formed due to a collision between them many years ago:
When this collision happened the iron cores merged to form the core of the Earth and the less dense material ended up being in the moon. There are two main areas of evidence for this:
1) Similarities in the composition of rocks on the Earth and moon
2) The Earth’s iron core is much bigger than the moon’s
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Asteroids
An “asteroid belt” lies between Mars and Jupiter. But what is an asteroid?
An asteroid is a rock left over from the formation of the solar system. They are between Jupiter and Mars because the gravitational attraction of Jupiter disrupted the formation of a planet.
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Asteroids
1) If an asteroid hit the Earth what effect would it have?
2) Many asteroids have already hit the Earth over many years – how do we know?
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Oh no…
Effects of Asteroid collisions The following things are possible consequences of an asteroid collision:
1) Extinction
2) Climate change
3) Sunlight blocked by dust
4) Craters
5) Widespread fires
As well as craters, evidence for asteroid collisions can also be seen by finding unusual elements in rocks and sudden changes in fossil numbers in adjacent rocks.
30/04/2015 Comets Comets are balls of dust and frozen gas. They have very elliptical orbits:
As the comet approaches the sun gases evaporate from it, forming a “tail”. This tail always faces AWAY from the sun. The comet also goes faster near the sun due to an increased gravitational attraction.
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Near Earth Objects A Near Earth Object (NEO) is an asteroid or comet on a possible collision course with the Earth.
How can we monitor and deal with Near Earth Objects?
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P2h The Big Bang
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Evidence about the origins of the universe…
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Source of light “Spectra”
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If you pass the light through a gas something different is seen…
helium
Some wavelengths of light are absorbed by the gas – an “absorption spectrum”.
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After
helium
If the light source is moving away the absorption spectra look a little different…
helium
Before
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The absorption lines have all been “shifted” towards the longer wavelength end (red end)…
After
Before
A similar effect happens with sound – this is called “The Doppler Effect”
This is called red shift. The faster the light source moves the further its light will be “shifted”
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Red Shift simplified
Basically, if I walk towards you I’ll look slightly more blue. Then, if I walk away
from you, I’ll look slightly more red!!
Let’s try it…
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Doppler Effect explained
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Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point.
This is the BIG BANG theory
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Red shift summary Light from other galaxies has a longer _________ than expected. This shows that these galaxies are moving ____ from us very quickly. This effect is seen to a greater extent in galaxies that are _______ away from us. This indicates that the further away the galaxy is, the ______ it is moving.
Words to use – faster, away, big bang, billion, wavelength, further
This evidence seems to suggest that everything in the universe is moving away from a single point, and that this process started around 15 _____ years ago. This is the ____ ________ Theory.
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Cosmic Microwave Background Radiation 30/04/2015
Further evidence of the Big Bang theory is Cosmic Microwave Background Radiation (CMBR) – this radiation comes from the Big Bang and fills the _________.
Basically, at the start of the universe, radiation was hot and had high _______. As time went on the ________and energy of this radiation dropped which turned it into to ________. This “background microwave _______” is all over the universe.
Words – microwaves, frequency, temperature, universe, radiation
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The Life Cycle of a Star
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Stage 1: Nebulae
A nebulae is a collection of dust, gas and rock.
Some examples of nebulae…
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Dark nebula
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Emission nebula
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Reflection nebula
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Planetary nebula (This nebula is smaller and will only form a planet)
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Gravity will slowly pull these particles together…
As they move inwards their gravitational potential energy is converted into heat and a PROTOSTAR is formed
Stage 2: Protostar
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Our sun is an example of a main sequence star – it’s in the middle of a 10 billion year life span
In a main sequence star the forces of attraction pulling the particles inwards are _________ by forces acting outwards due to the huge __________ inside the star.
Stars are basically ________ reactors that use _______ as a fuel. During its main sequence a star will release energy by converting hydrogen and helium (light elements) into _________ elements and this is why the universe now contains a number of heavier elements.
Words – heavier, balanced, hydrogen, nuclear, temperatures
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Eventually the hydrogen and helium will run out. When this happens the star will become colder and redder and start to swell…
If the star is relatively small (like our sun) the star will
become a RED GIANT
If the star is big (at least 4 times the size of our sun) it will become a
RED SUPERGIANT
Stage 4: Red Giant
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What happens at this point depends on the size of the star…
1) For SMALL stars the red giant will collapse under its own gravity and form a very dense white dwarf:
Stage 5: The Death
White dwarf Black dwarf Red giant
30/04/2015 30/04/2015 2) If the star was a RED SUPERGIANT it will shrink and then EXPLODE, releasing massive amounts of energy, dust and gas.
After Before
This explosion is called a
SUPERNOVA
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The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR.
If the star is big enough it could become a BLACK HOLE instead.
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Black Holes A black hole is an object that is so small and dense that its escape velocity is greater than the speed of light. In other words, not even light can escape its gravitational pull.
Fascinating
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The dust and gas thrown out by a supernova can be used to form a new star…
Stage 6: Second generation stars
Our sun is believed to be a “______ ______ star” – this is because it contains some __________ elements along with hydrogen and ________. These heavier elements would have been the products of a previous star that have been thrown out by a ________. These heavier elements are also found on planets, indicating that they might have been made from remains of previous _______ as well.
Words – helium, heavier, second generation, stars, supernova
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The Life Cycle of a Star summary
Protostar
Main sequence
Red super giant
Supernova
Red giant
White dwarf
Black dwarf Neutron star Black hole
Basically, it all depends on the size of the star!
SMALL stars
BIG stars
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Our understanding of the universe
Ptolemy, AD 90-168
Copernicus, 1473-1543
Up until the 16th Century people believed that the Earth was the centre of the universe – this is called the “Geocentric model” and I made a model of the universe based on it.
I published my “On the revolutions of the celestial spheres” just before my death and showed that the Earth and other planets orbit around the sun – the “Heliocentric model”.
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Evidence for the Heliocentric Model
Galileo, 1564-1642
Jupiter and its moons, as seen through a telescope
The orbits of these moons
I helped develop the modern telescope and made measurements with it that proved that the Copernican model of the solar system was correct but a lot of people didn’t like it because the old Catholic Church didn’t like it.
