Transcript P2 Living for the Future

12/04/2017
Living for the Future
(OCR Gateway Additional Science)
W Richards
P2a Collecting Energy from the Sun
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Solar Panels and Thermal Towers
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What are the
advantages and
disadvantages of solar
power?
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Using Solar Energy in remote places
Solar Energy
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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
Other ways to use solar energy
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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?
Passive solar heating
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“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
P2b Generating Electricity
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DC and AC
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V
DC stands for “Direct
Current” – the current only
flows in one direction.
Batteries supply DC.
Time
1/50th s
AC stands for “Alternating
Current” – the current
changes direction 50 times
every second (frequency =
50Hz). Household
electricity is AC
230V
T
V
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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
AC Generator
N
S
N
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S
Current
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
Time
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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
Efficiency
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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%
Some examples of efficiency…
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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?
Efficiency of Power Stations
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Heat
100J
Boiler
85J
Heat
Heat
Turbine
35J
Kinetic
Heat
Generator
30J
Electrical
What is the efficiency at each stage of this power station?
P2c Global Warming
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The following two graphs are taken from Wikipedia. What do
they imply?
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The Greenhouse Effect
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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
The Changing Greenhouse Effect
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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
Volcanoes
Factory pollution
Differing views on Global Warming
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The following data shows global warming figures and
projections from different research centres. What do you
notice?
P2d Fuels for Power
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Fuels
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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.
Nuclear power stations
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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”
Biomass
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“Biomass” is a term used to describe anything that can be
grown or biologically made and then burned as a fuel:
Non-renewable energy sources
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Advantages
Disadvantages
Cheap fuel costs
Costs a lot of
money to
decommission a
nuclear plant
Good for “basic
demand”
Reliable
Coal, oil, gas and
nuclear
Fuel will run
out
Short start-up time for
gas and oil
Nuclear produces little
pollution
Pollution – CO2 leads to
global warming and SO2
leads to acid rain
Renewable energy sources summary
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Advantages
Disadvantages
Zero fuel costs
Unreliable
(except for
hydroelectric)
Don’t produce
pollution
Hydroelectric
is good for a
“sudden”
demand
Solar is good for
remote locations
(e.g. satellites)
Wind, tidal,
hydroelectric and solar
Expensive
to build
Ugly and the energy
produced by them is very
“dilute”
Energy and Power
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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
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)
P
T
Some example questions
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1) What is the power rating of a light bulb that transfers
120 joules of energy in 2 seconds?
60W
2) What is the power of an electric fire that transfers
10,000J of energy in 5 seconds?
2KW
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?
0.2MW
4) How much energy does a 150W light bulb transfer in a)
one second, b) one minute?
150J,
9KJ
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?
120KJ
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?
630MJ
The Cost of Electricity
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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
The Cost of Electricity
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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
72p
2) A 0.2kW TV left on for 5 hours
12p
3) A 0.1kW light bulb left on for 10 hours
12p
4) A 0.5kW hoover left on for 1 hour
6p
Electricity is cheaper at night time (around 5p per unit) –
how much would these devices cost at night time?
Power
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Power is “the rate of doing work”.
The amount of power being used in
an electrical circuit is given by:
Power = voltage x current
in W
in V
in A
P
V
I
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?
500W
2) An electric fire has a power rating of 2KW. If it runs on a
voltage of 230V what is the current?
8.7A
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?
400MW
The National Grid
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Electricity reaches our homes from power stations through the National
Grid:
Power station
Step up
transformer
Step down
transformer
Homes
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
P2e Nuclear Radiations
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The structure of the atom
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ELECTRON –
negative, mass
nearly nothing
NEUTRON –
neutral, same
mass as
proton (“1”)
PROTON –
positive, same
mass as
neutron (“1”)
Introduction to Radioactivity
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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”.
Background Radiation
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13% are
man-made
Radon gas
Food
Cosmic rays
Gamma rays
Medical
Nuclear power
Blocking Radiation
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Each type of radiation can be blocked by different materials:



Sheet of
paper
Few mm of
aluminium
Few cm of
lead
Ionisation
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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.
Uses of Alpha Radiation
Smoke detectors
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Alpha
emitter
+ve electrode
-ve electrode
Alarm
Ionised air particles
If smoke enters here a
current no longer flows
Uses of Beta Radiation
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Beta
detector
Rollers
Paper
Beta
emitter
Uses of Gamma Radiation
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Sterilising medical instruments
Gamma rays can be used to kill and sterilise
germs without the need for heating.
Other uses of radioactivity
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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
The radiation from the radioactive source is picked up above
the ground, enabling the leak in the pipe to be detected.
Tracers can also be used to develop
better plant fertilisers and in
medicine to detect tumours:
Handling Radioactive Materials
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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.
Disposing of radioactive waste
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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:
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 containers are then kept
in stores, often _________.
Words – glass, steel, underground, radioactive
P2f Exploring our Solar System
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The Solar System summarised
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What makes up our solar system? Complete the following mind
map with what you now about each object:
The solar system
The eight planets of our Solar System
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Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
As well as the eight planets, the solar system is also made
up of asteroids, dwarf planets, comets and moons
Distances in space
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Definition – a “light year” is the distance covered by light every year
The Sun, our closest star, is 1.6x10-5 light years
away from us.
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.
The Andromeda Galaxy (our closest galaxy)
– approximately 2.5 million light years away
Solar systems, galaxies and the Universe
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Our planet (around 13,000km diameter and 4500 million
years old) is pretty small compared to...
OUR SUN (100 times wider
and 4.6 billion years old),
which is small compared to…
THE UNIVERSE, which
contains billions of galaxies and
is 14,000 million years old.
THE MILKY WAY, which
contains at least 200 billion
stars and is 100,000 light
years across, which is small
compared to…
How our Earth and the Sun
compare to others…
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Elliptical Orbits
Ellipse
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The Earth is kept in orbit by 2 things…
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This is called a
“centripetal force”
Gravity
…and by the
fact that it is
moving at a high
velocity
Searching for Aliens
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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?
Space Travel
Advantages
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Disadvantages
Manned space
travel
Unmanned space
travel
P2g Threats to the Earth
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The moon
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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
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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Effects of Asteroid collisions
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The following things are possible consequences of an asteroid
collision:
Oh no…
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.
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
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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?
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”.
If the light source is moving away the absorption
spectra look a little different…
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Before
helium
helium
After
The absorption lines have all been “shifted”
towards the longer wavelength end (red end)…
This is called red
shift. The faster
the light source
moves the further
its light will be
“shifted”
Before
After
A similar effect happens with sound –
this is called “The Doppler Effect”
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Red Shift simplified
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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
Red shift summary
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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.
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.
Words to use – faster, away, big bang,
billion, wavelength, further
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Cosmic Microwave Background Radiation
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
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)
Stage 2: Protostar
Gravity will slowly pull these
particles together…
As they move inwards
their gravitational
potential energy is
converted into heat and
a PROTOSTAR is formed
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Stage 3: Main Sequence
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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.
Our sun is an example of a main sequence star –
it’s in the middle of a 10 billion year life span
Words – heavier, balanced, hydrogen, nuclear, temperatures
Stage 4: Red Giant
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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 5: The Death
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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:
Red giant
White dwarf
Black dwarf
2) If the star was a RED
SUPERGIANT it will shrink and
then EXPLODE, releasing massive
amounts of energy, dust and gas.
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This explosion is
called a
SUPERNOVA
Before
After
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.
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If the star is big
enough it could
become a BLACK
HOLE instead.
Black Holes
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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
Stage 6: Second generation stars
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The dust and gas thrown out by a supernova can be used to
form a new star…
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
The Life Cycle of a Star summary
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Protostar
SMALL
stars
BIG
stars
Main sequence
Red giant
Red super giant
White dwarf
Supernova
Black dwarf
Neutron star
Basically, it all depends on the size of
the star!
Black hole
Our understanding of the universe
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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.
Ptolemy, AD 90-168
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”.
Copernicus, 1473-1543
Evidence for the Heliocentric Model
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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.
Galileo, 1564-1642
Jupiter and its moons, as seen
through a telescope
The orbits of
these moons