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OCR 21ST CENTURY
SCIENCE
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THE EARTH IN THE UNIVERSE
INCLUDING:
Earth, stars, galaxies and space
How the Earth is changing
Seismic waves
Earth, stars, galaxies and space
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Earth, stars, galaxies and space
The Earth is one of the eight planets orbiting the Sun, and
there are many other members of the Solar System
including asteroids, moons and planets. Data provides the
answers to many questions on this subject, but some
questions remain unanswered.
The Earth and the Universe
The Universe is considered to be everything there is, though
most of it is thought to be empty.
Much is now known about the Earth and the place of the Earth in
the Universe, for example:
the diameter of the Earth is 12,800km (7,953 miles)
the diameter of the Sun is 109 times that of the Earth’s
the Earth is 150 million km (93 million miles) from the Sun
the distance to the nearest star is four light years.
Earth, stars, galaxies and space
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The Solar System
The Earth is just one of the eight planets orbiting the
Sun, which is a star. The orbits all lie in the same
plane, and the planets all go round in the same
direction.
There are many other members of our Solar System:
asteroids are much smaller than planets, and orbit the
Sun. Most of the asteroids are between the planets
Mars and Jupiter, but some come close to the Earth
moons orbit planets. Most are tiny. Only a few are as
large as our Moon, which is nearly a sixth of the
diameter of the Earth
comets have different orbits to those of planets,
spending much of their orbital time far from the Sun.
Comets are similar in size to asteroids, but are made
of dust and ice. The ice melts when the comet
approaches the Sun, and forms the comet’s tail.
The Sun
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The Sun
Nearly all of the mass in our Solar System is in the Sun. The Sun
is very large. Its diameter is 109 times the Earth's. The Sun is the
source of nearly all the energy we receive. For many years, it
was a mystery as to where this came from and this baffled the
leading scientists. It is now understood that the nuclear fusion is
the energy source. In nuclear fusion, smaller nuclei come
together and form larger nuclei. For example hydrogen nuclei are
joined together to make helium nuclei. This releases enormous
amounts of energy.
hydrogen nucleus + hydrogen nucleus → helium nuclei
In stars larger than our Sun helium nuclei can be fused together
to create larger atomic nuclei. As the Earth contains many of
these larger atoms, like carbon, oxygen, iron, etc, scientists
believe that our Solar System was made from the remains of an
earlier star.
Stars form from massive clouds of dust and gas in space
Gravity pulls the dust and
gas together
How stars and planets are formed
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How stars and planets are formed
As the gas falls together, it gets hot. A star forms
when it is hot enough for anuclear fusion
reaction to start. This releases energy, and keeps
the star hot. The outward pressure from the
expanding hot gases is balanced by the force of the
star's gravity. This happened about 5 billion years
ago. This is quite recent in the history of the
Universe, which is currently believed to be 14 billion
years old.
Gravity pulls smaller amounts of dust and gas
together, which form planets in orbit around the star.
Looking at the sky
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Looking at the sky
The radiation that distant stars and galaxies produce gives us information about the
distances to stars, and about how they are changing. In the future, this may allow us to find
out if life exists on planets around some of these stars.
Everything we know about stars and galaxies has come from the light, and other radiations,
that they give out. This has become more difficult to see from the Earth’s surface, as light
pollution from towns and cities interferes with observations of the night sky.
Looking at the sky with the naked eye shows the Sun, Moon, stars, planets and a few
cloudy patches called nebulae. When telescopes were invented and developed,
astronomers could see that some of the nebulae were in fact groups of millions of stars.
These are galaxies.
Parallax
Powerful telescopes allowed astronomers to answer a question that had baffled scientists
since the astronomer Copernicus (1473-1543) first suggested that the Earth moved around
the Sun. If the Earth moves, you would expect to see a different view of the stars at
different times of the year, in the same way as the room you are in looks slightly different if
you move your head to one side. That is to say everything seems to move in the opposite
direction to your head, but the objects close to you seem to move more. This effect is
called parallax. So if the Earth was moving, why did the stars always look the same?
The answer to the question was revealed by more powerful telescopes. These showed that
nearby stars do seem to move from side to side and back every year when compared with
very distant stars, but that the amount of movement is tiny.
Finding the distance of a star using parallax
The second nearest star to us is Proxima Centauri. The Sun is the
nearest.
It seems to move through an angle of 1.5 seconds between January
and June. As one second = 1/60 of a minute, and one minute = 1/60
of a degree, this tiny movement, which is less than a thousandth of
the diameter of the Moon, needed powerful telescopes and
accurate measurement to observe.
Light Pollution & telescopes
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In the last 200 years, it has become very difficult to make
astronomical observations in industrialised countries such as the
UK. This is not just because of cloudy weather or air pollution. It
is due to the bright lights found in cities and towns, and on roads.
This light pollution means that it is hard for many people to see
more than a few of the very brightest stars at night.
Telescopes
Telescopes are now placed in the few remote, dark places left on
our planet, or out in orbit around the Earth.
The Very Large Telescope is part of the Paranal Observatory
that is built on top of the Cerro Paranalmountain, which is 2,635
m high, in the Atacama Desert in Chile.
More On Telescopes
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Telescopes in space, such as the Hubble
Space Telescope, can observe the whole
sky. They are above light pollution and above
dust and clouds in the atmosphere. However,
they are difficult and expensive to launch and
maintain. If anything goes wrong, only
astronauts can fix them.
Beyond Our Solar System
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Beyond our Solar System
The Sun is 150 million km(93 million miles) from the Earth, but
that’s a tiny distance compared with the distance to other stars,
or other galaxies. Larger units of distance are used for these
measurements. One popular measurement is the light-year.
Light-years
A light-year is the distance light travels in a year. Light travels
very fast (300,000 km/186,282 miles per second), and takes only
about eight minutes to reach us from the Sun. It takes over four
years to reach us from the next nearest star (Proxima Centauri),
and 100,000 years to cross the Milky Way galaxy. We say that
the distance to the next nearest star is four lightyears, and the
diameter of the Milky Way is 100,000 light years.
The most distant galaxies observed are about 13,000 million
light-years away. However, measuring distances to other stars,
and to very distant galaxies, is not easy, so the data is uncertain.
Measurement uncertainties
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Measurement uncertainties
When initial distances to stars were being established more than one
method was employed. After establishing distances of nearby stars
using the parallax method, the 'brightness method' was used to
approximate distances to further stars. Other methods were also used.
Each method had its own assumptions. For example, with the parallax
method an assumption made is that during the total time in which the
measurement is taking place, distance remains constant between the
two stars.
As methods were reliant on each other, a certain level of uncertainty is
found in the results.
A cluster of young stars in the Small Magellanc Cloud
dwarf galaxy
Ideas about Science
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Ideas about science - developing explanations
Different explanations can be developed to illustrate the theory
that the dinosaurs were destroyed by an asteroid impact.
Data and explanations
Data statements tell you facts, and may contain measurements.
For example, look at these three statements:
asteroids are small objects orbiting the Sun
some asteroids have orbits close to the Earth
the dinosaurs died out at about the same time as a large crater
was made in Mexico.
Explanations seek to explain the data, and formulating an
explanation requires imagination and creativity. One explanation
is that an asteroid collision may have killed off the dinosaurs. The
asteroid impact would have created dust that blocked out light
and heat from the Sun.
Predictions
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Predictions
A good explanation will explain data, and link together things thatwere not thought to be
related. It should also make predictions.
asteroids often contain the rare metal iridium - data
a huge asteroid impact would send iridium dust throughout the world - prediction
sedimentary rocks from the time the dinosaurs died out contain iridium - data
when the asteroid crashed, the iridium came from the dust tha tblocked out the Sun explanation.
Data and predictions can be used to test an explanation, but you have to be careful. When
an observation agrees with the prediction, it makes you more confident in the explanation,
but it does not prove that the explanation is true.
The opposite is also correct. When an observation disagrees with a prediction, it makes
you less confident in the explanation, but it does not prove that the explanation is wrong.
The data may be faulty.
The asteroid theory is not the only one about the death of the dinosaurs. Other are:
there were huge volcanic eruptions in India at the time the dinosaurs died out - data
big volcanic eruptions cause dust clouds thatblock out the Sun - data
the big Indian eruptions could have killed out the dinosaurs by cooling the Earth explanation.
Unanswered questions
Not all scientific questions have answers at this time. For some of the questions there is not
enough data yet. An example of this is the question: is there life on distant planets? For
other questions, there may never be the data you need. An example of this is: what
happened before the ‘Big Bang’ when the Universe was created?
Galaxies
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Galaxies
Galaxies contain thousands of millions of stars. For many years, it was thought that
our galaxy, which is the Milky Way, was the only one that existed, and that the
blurry nebulae that could be seen were clouds of dust and gas in the Milky Way.
Observations of many of these nebulae by astronomers such as Edwin Hubble
showed they were in fact galaxies outside the Milky Way, and that distant galaxies
are all moving away from us.
The beginning and end of the Universe
Hubble’s observations led to the ‘Big Bang’ explanation of the beginning of
theUniverse, and set a date for this at 14,000 million years ago.
There are many questions left unanswered about the beginning and end of the
Universe. Observations suggest it contains a lot of ‘dark matter’ that cannot be seen,
and this is not yet clearly understood.
Perhaps the Universe will continue to expand in the way it is at the moment. Perhaps
gravity will eventually win and pull all the fleeing galaxies back together again. Better
observations of very distant galaxies and a better understanding of the mysterious
‘dark matter’ are needed before these will be understood.
Hubble’s Law- Higher tier
The astronomer Edwin Hubble (1889-1953) measured the distance to many galaxies,
and also the speeds with which they are moving away from us. He found a strong
correlation between these factors.
Some galaxies do not fit exactly on the line of correlation
This correlation is summed up in Hubble’s Law which says that
the speed at which a galaxy moves away from us is proportional
to its distance from us.
The causal link which explains this law is that space itself is
expanding.
As the Universe expands, galaxies that are already further apart
will increase in separation even more, and so move away at
higher speeds.
Age of the Universe
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Age of the Universe
The development of powerful telescopes allowed astronomers to see
distant galaxies. The light observed was shifted towards the red end of
the spectrum. This phenomenon is known as red-shift. The degree to
which light has been shifted indicates how fast the galaxies are moving
away.
In general, the further away the galaxy is, the faster it is moving away
from the Earth. The motions of the galaxies themselves suggest that
space itself is expanding.
It is estimated that the Universe is approximately 13.7 billion years old.
Evidence suggests that our Solar System formed around 4.5 billion
years ago, so it is around one-third the age of the Universe.
The eventual fate of the Universe is hard to predict due to the
uncertainty in measuring such large distances and studying motion of
distant objects. A better idea of the mass of the Universe would lead to
better predictions.
How the Earth is changing
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The theory of plate tectonics is now well established. Continental drift
is happening as tectonic plates move, with earthquakes and volcanoes
often occurring around their edges.
Evidence from rocks
Rocks provide evidence for changes in the Earth. In 1785 James Hutton
presented his idea of a rock cycle to the Royal Society. He detailed ideas
oferosion and sedimentation taking place over long periods of time,
making massive changes to the Earth’s surface.
Geologists can use other evidence from the rocks themselves such as:
looking at cross-cutting features (rock that cuts across another is younger)
using fossils (species existed/ became extinct during certain time periods)
deepness of the rock (younger rocks are usually on top of older ones).
This kind of evidence only shows that some rocks are older than others. To
get a more accurate idea of the age of rocks radioactive dating is used.
Wegener’s theory
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Wegener’s theory
Alfred Wegener (1880 - 1930)
Alfred Wegener proposed the theory of continental
drift at the beginning of the 20th century. His idea
was that the Earth's continents were once joined
together, but gradually moved apart over millions of
years. It offered an explanation of the existence of
similar fossils and rocks on continents that are far
apart from each other. But it took a long time for the
idea to become accepted by other scientists.
Before Wegener
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Before Wegener
Before Wegener developed his theory, it was thought that
mountains formed because the Earth was cooling down,
and in doing so contracted. This was believed to form
wrinkles, or mountains, in the Earth's crust. If the idea was
correct, however, mountains would be spread evenly over
the Earth's surface. We know this is not the case. The
heating effect of radioactive materials inside the Earth
prevents it from cooling.
Wegener suggested that mountains were formed when the
edge of a drifting continent collided with another, causing it
to crumple and fold. For example, the Himalayas were
formed when India came into contact with Asia.
This slideshow explains Wegener's theory.
Earth around 200 million years ago, at
the time of Pangaea
The single landmass began to
crack and divide, due to the
slow currents of magna beneath
it
The positions of the continents today
Wegener’s evidence
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Wegener’s evidence for continental drift was that:
the same types of fossilised animals and plants are
found in South America and Africa
the shape of the east coast of South America fits
the west coast of Africa, like pieces in a jigsaw
puzzle
matching rock formations and mountain chains are
found in South America and Africa.
Ideas about science - the scientific
community
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Publishing and peer review
Scientists report their ideas to the scientific community. They
present them at conferences and then write them up in journals
or books.
At conferences, other scientists will listen and debate the new
ideas. Before journals or books are published, other expert
scientists read the new ideas and decide if they are sensible.
This is called peer review.
Wegener presented his ideas at a conference in 1912, and then
published them in a book in 1915.
Repeating experiments
Scientists do not usually accept the results of experiments until
someone else has repeated them to get the same results. It is
hard to set up experiments in geology and astronomy, so new
theories need support from different observations.
MORE
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Different explanations
Data often allows more than one possible explanation, so different scientists can
have different explanations for the same observations.
Wegener’s ideas could certainly explain similar fossils turning up in different
continents, but other geologists thought that there were once ‘land bridges’ between
continents, allowing animals to travel between them.
The different backgrounds of different scientists can affect their judgements, so they
may have quite different explanations for the same data.
Wegener was trained as an astronomer and a meteorologist. Many geologists did not
think that he had the right background to judge geological theories.
Wagener's new explanation becomes accepted
The old geological theory explained mountains as wrinkles made by the Earth
shrinking as it cools down.
There was no clear explanation of how continents could move about - a new scientific
explanation often needs new supporting evidence to convince scientists that it is
correct.
Then, in the 1950s, evidence from magnetism in the ocean floor showed that the
seafloors were spreading by a few centimetres each year. This showed movement of
large parts of the Earth’s crust, now called tectonic plates. This new evidence allowed
Wagener's theory to be accepted.
A scientific explanation is rarely abandoned just because some data does not
correspond to it, but it is safer to stick with a theory that has worked well in the past.
Seafloor spreading
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Seafloor spreading
In the centres of many oceans, there are mid-ocean
ridges. At these places, thetectonic plates are
moving apart. Molten material, known
as magma from inside the Earth oozes out and
solidifies. This movement of the mantle is referred to
as convection due to heating by the core of the
Earth. This process is calledseafloor spreading. It
results in seafloors spreading by a few centimetres
each year.
Inside the Earth
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Inside the Earth
All our evidence for changes in the Earth comes
from looking at rocks. Folds and fossils
in sedimentary rocks, radioactive dating and the
weathering of ancient craters show that the oldest
rocks are about 4000 million years old. That means
the Earth must be at least as old as this.
The only thing that we have been able to observe
directly is the Earth’s crust, which is the very thin
outer rocky layer.
Evidence from earthquakes shows that the Earth
has a very dense core surrounded by a
solid mantle.
Cross section showing structure of the Earth
The Earth is almost a sphere. These are its main layers, starting with the
outermost:
The crust, which is relatively thin and rocky
The mantle, shown here as dark red, which has the properties of a solid, but
can flow very slowly
The outer core, shown as orange, which is made from liquid nickel and iron
The inner core, shown as yellow, which is made from solid nickel and iron
The Earth's magnetic field - Higher tier
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The Earth's magnetic field - Higher tier
The typical speed of seafloor spreading is slow:
about 10 cm per year. When themagma oozing out
of mid-ocean ridges solidifies into rock, the rock
records the direction of the Earth’s magnetic field.
The Earth’s magnetic field changes with time, and
sometimes even reverses its direction. These
changes are recorded in the rocks. The same
magnetic patterns are seen on both sides of the
mid-ocean ridges.
Plate tectonics - Higher tier
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Plate tectonics - Higher tier
The Earth’s crust, together with the upper region of the mantle, consists of
huge slabs of rock called tectonic plates. These fit together rather like the
segments on the shell of a tortoise.
Although the mantle
below the tectonic
plates is solid, it does
move. This movement
is very, very slow – a
few centimetres every
year. This means that
the continents have
changed their
positions over millions
of years.
Movement of tectonic plates - Higher tier
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Movement of tectonic plates - Higher tier
Volcanoes, mountains and earthquakes occur at the edges of tectonic
plates - their creation depends on the direction the plates are moving.
Volcanoes
If the plates are moving apart, as at mid-ocean ridges, volcanoes are
produced as molten magma is allowed to escape. This happens in
Iceland.
Mountains
If the plates are moving towards each other, the edges of the plates
crumple, and one plate ‘dives’ under the other. This is
called subduction. It produces mountains, like the Himalayas. The
friction of the movement can also melt rocks and produce volcanoes.
This is also part of the rock cycle, because the plate that dives under
the other one becomes part of the mantle and emerges much later from
volcanoes and in seafloor spreading.
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There are two other ways in which mountains can
be formed. At destructive margins mountain chains
can be formed as plates push against each other. If
an ocean closes completely then continents can
collide. This occurs slowly but the collision would still
result in the formation of a mountain chain.
Earthquakes
If the plates are moving sideways, stresses build
up at the plate boundary. When the stress reaches
some critical value, the plates slip suddenly, causing
an earthquake. It is hard to predict when such an
event may happen.
Detecting wave motions
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Detecting wave motions
A seismometer detects the vibrations of an
earthquake.
The vibrations of an earthquake are detected
using a seismometer that records the results
in the form of a seismogram.
The vibrations that are detected from the site
of an earthquake are known as seismic
waves.
Seismic waves
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Vibrations from an earthquake are categorised as P or S
waves. They travel through the Earth in different ways and
at different speeds. They can be detected and analysed.
P and S waves
A wave is a vibration that transfers energy from one place to
another without transferring matter (solid, liquid or gas). Light and
sound both travel in this way.
Energy released during an earthquake travels in the form of
waves around the Earth. Two types of seismic wave exist, P- and
S-waves. They are different in the way that they travel through
the Earth.
P-waves (P stands for primary) arrive at the detector first. They
are longitudinal waves which mean the vibrations are along the
same direction as the direction of travel. Other examples of
longitudinal waves include sound waves and waves in a
stretched spring.
Amplitude, wavelength and frequency
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Amplitude, wavelength and frequency
You should understand what is meant by the amplitude,
wavelength and frequency of a wave.
Amplitude
As waves travel, they set up patterns of disturbance. The
amplitude of a wave is its maximum disturbance from its
undisturbed position. Take care: the amplitude is not the
distance between the top and bottom of a wave. It is the
distance from the middle to the top.
Wavelength and Frequency
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Wavelength
The wavelength of a wave is the distance between a point on
one wave and the same point on the next wave. It is often
easiest to measure this from the crest of one wave to the crest of
the next wave, but it doesn't matter where as long as it is the
same point in each wave.
Frequency
The frequency of a wave is the number of waves produced by a
source each second. It is also the number of waves that pass a
certain point each second. The unit of frequency is the hertz
(Hz). It is common for kilohertz (kHz), megahertz (MHz) and
gigahertz (GHz) to be used when waves have very high
frequencies. For example, most people cannot hear a highpitched sound above 20kHz, radio stations broadcast radio
waves with frequencies of about 100MHz, while most wireless
computer networks operate at 2.4GHz.
Wave Speed
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Wave speed
Wave speed is the velocity at which each wave crest moves and
is measured in metres per second (m/s). The wave speed only
depends on the material the wave is travelling through. The
distance travelled by a wave is calculated using this equation:
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Distance = speed x time
The speed of a wave - its wave speed (metres per second, m/s)is related to its frequency (hertz, Hz) and wavelength (metre, m),
according to this equation:
wave speed = frequency x wavelength
For example, a wave with a frequency of 100Hz and a
wavelength of 2m travels at 100 x 2 = 200m/s.
The speed of a wave does not usually depend on its frequency or
its amplitude.
Radiation Life – P2
INCLUDING:
• Electromagnetic radiation
Benefits and risks
Global warming
Waves and communication
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Light is one of the family of radiations called the electromagnetic
spectrum. Some types of electromagnetic radiation are used to
transmit information such as computer data, telephone calls and
TV signals.
The electromagnetic spectrum
Refraction from a prism
The pattern produced when white light shines through a prism is called
the visible spectrum.
The prism separates the mixture of colours in white light into the
different colours red, orange, yellow, green, indigo and violet.
In fact, visible light is only part of the electromagnetic spectrum. It’s the
part we can see.
Photons and ionisation
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Photons and ionisation
Electromagnetic radiation comes in tiny ‘packets’ called photons.
The photons deliver different quantities of energy, with radio photons delivering
the smallest amount, and gamma photons delivering the greatest amount of
energy.
A higher frequency of electromagnetic radiation means more energy is
transferred by each photon.
If the photons have enough energy, they can break molecules into bits called
ions. This is called ionisation. These types of radiation are called ionising
radiation. This radiation can remove electrons from atoms in its path.
In the electromagnetic spectrum only the three types of radiation, which have
the photons with most energy, are ionising. These are ultraviolet, Xrays andgamma rays.
Damaging to health - Higher tier
The ions produced when ionising radiation breaks up molecules can take part in
other chemical reactions. If these chemical reactions are in cells of your body,
the cells can die or become cancerous. This is the reason that ionising radiation
can be damaging to health.
Energy and intensity
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Energy and intensity
The intensity of electromagnetic radiation is the energy arriving at
a square metre of surface each second. This depends on two
things: the energy in each photon, and the number of photons
arriving each second.
To have the same intensity, a beam of red light would need ten
times as many photons as a beam of ultraviolet, and a beam of
microwaves would need a million times as many.
Energy of 1 ultraviolet photon = Energy of 10 red
photons = Energy of 1,000,000 microwave photons
Absorption of radiation - Higher tier
All forms of electromagnetic radiation deliver energy. This will
heat the material that absorbs the radiation. The amount of
heating depends on the intensity of the radiation, and also
the length of time the radiation is absorbed for.
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Electromagnetic radiation
An object which gives out electromagnetic radiation is called
a source of radiation.
Something which is affected by the radiation is a detector.
Lower intensity of radiation
Further from the source, the detector receives a lower intensity of
radiation.
As the photons
spread out from the
source, they are
more thinly spread
out when they reach
the detector. The
intensity may also
decrease with
distance due to
partial absorption by
the medium it travels
through.
Ionising radiation
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Ionising radiation
Ionising radiation can break molecules into smaller
fragments. These charged particles are called ions.
As a result, ionising radiation damages substances
and materials, including those in the cells of living
things. The ions themselves can take part in
chemical reactions, spreading the damage.
Ionising radiation includes:
ultraviolet radiation, which is found in sunlight
x-rays, which are used in medical imaging machines
gamma rays, which are produced by some
radioactive materials.
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Non-ionising radiation
Not all types of electromagnetic radiation are ionising. Radio
waves, light and microwaves are among them.
Microwaves
Microwaves are used to heat materials such as food. The
molecules in the material absorb the energy delivered by the
microwaves. This makes them vibrate faster, so the material
heats up.
The heating effect increases if:
the intensity of the microwave beam is increased
the microwave beam is directed onto the material for longer.
So you need to cook food for longer in a less powerful microwave
oven. This is why they have power ratings, and food labels
recommend different cooking times depending on this.
Atmosphere
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Radiation that is not absorbed by the atmosphere reaches
the Earth's surface and warms it, leading to the greenhouse
effect. Some radiation, such as ultraviolet, exposes our skin
to harmful rays and puts us at risk of developing skin
cancer.
The atmosphere
Some radiation of the electromagnetic spectrum is absorbed by
the atmosphere, but some is transmitted.
Light, some infrared, some ultraviolet, and microwaves, pass
through the atmosphere and reaches the Earth’s
surface. Gamma rays, X-rays, most of the ultraviolet and some of
the infrared are absorbed by the atmosphere and do not reach
the Earth’s surface.
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Infrared
Infrared from the Sun reaches the Earth’s surface and warms it.
The warm Earth emits some infrared radiation, and some of this
is absorbed by gases in the atmosphere. This is called the
greenhouse effect. If there was no greenhouse effect, the Earth
would be too cold for life as we know it.
Photosynthesis
Light from the Sun reaching the Earth’s surface provides the
energy for plants to produce food by photosynthesis.
Photosynthesis replaces carbon dioxide in the atmosphere with
oxygen. This reverses the process of respiration.
Microwaves
The atmosphere transmits
microwaves, and these can be
used to communicate with
satellites.
•Light from the sun reaching earth
Radiation and cell damage
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Radiation and cell damage
Any radiation absorbed by living cells can damage them by
heating them. However, ionising radiations are more likely to
damage living cells. This is because photons of ionising radiation
deliver much more energy. They can easily kill cells, and can
also cause cancer by damaging the DNA in the nucleus of a cell.
Effects of microwaves
Microwaves in the environment may be harmful, but there is no
agreement on this. They are not ionising, and so cannot cause
cancer in the way that ultraviolet, X-rays orgamma rays do.
Microwave ovens work because the food contains water
molecules which are made to vibrate by the microwaves. This
means that food absorbs microwaves and gets hot. The
microwaves cannot escape from the oven, because the metal
case and the metal grid on the door reflect microwaves back into
the oven.
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Some people think that mobile phones, which
transmit and receive microwaves, may be a
health risk. This is not accepted by
everyone, as the intensity of the microwaves
is too low to damage tissues by heating, and
microwaves are not ionising.
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Ultraviolet
Umbrellas can be useful in the sun as well as the rain
One health risk which is definitely present in our environment is
ultraviolet, in sunlight. Not much of the ultraviolet reaching the
Earth gets to us, because the ozone layer high up in the
atmosphere absorbs most of it. In the summer, it is wise to use
sunscreens and clothing to absorb ultraviolet, and prevent it
reaching the sensitive cells of the skin.
The ozone layer - Higher tier
Ozone molecule formation
The ozone layer absorbs ultraviolet because ultraviolet ionises
the ozone, which then changes to oxygen. This chemical change
is reversible, and the oxygen changes back to ozone.
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Ideas about science - risk
Scientific or technological developments often introduce new risks.
Chemicals used in aerosol spray cans and fridges gradually made
their way up to the ozone layer when released into the atmosphere,
and removed some of it. This has increased the intensity of
the ultraviolet radiation reaching the Earth. These chemicals are not
used any more, and the ozone layer is gradually returning to normal.
However, this will take a number of yers more.
It is important to be able to assess the size of risk in any activity. No
activity is completely safe.
The consequence of too much ultraviolet – skin cancer – often does
not appear until much later in life, so it doesn't seem a real risk to
young people.
It is difficult to assess how much ultraviolet you are receiving when
you are sunbathing. If you feel hot, that is because of the infrared,
not the ultraviolet
Weather forecasts now inform you of the intensity of ultraviolet
radiation.
Benefits
For most risky activities, there are benefits as well as risks:
sunbathing produces a sun tan, which many people find more
attractive
some ultraviolet is good for you, as it produces vitamin D in the skin.
Read on if you are taking the higher tier paper.
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Making a judgement - Higher tier
To make a judgement about a possible bad outcome you need to
consider two factors:
What is the chance of the outcome happening?
What is the consequence of that outcome?
The precautionary principle
The ‘precautionary principle’ tells you to avoid any activity if serious
harm could arise.
parents may insist that their children are not allowed out on the
beach at all in the summer months.
The real risk may be very different from the perceived risk ie the
risk that you think is there.
you can’t see ultraviolet, and the word ‘radiation’ sounds frightening
to many people. This makes the risk seem worse than something
you can see, and which is more familiar
Some parents may assume that summers are no different from
when they were young, so there is no danger to their children
Other parents may be very alarmed by stories of increases in skin
cancer, and not let their children out in sunny weather at all
Sometimes risk should be regulated by governments and other
public bodies. This usually applies to an organisation which is
responsible for its employees. In some situations this may be
controversial.
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Types of radiation from the electromagnetic spectrum make
life on Earth possible, but some have hazards associated
with them. These hazards need to be carefully considered,
and the evidence weighed up in order to reach a scientific
explanation.
Greenhouse gases
Some gases in the Earth’s atmosphere absorb infrared radiation.
One of these is carbon dioxide. Even though carbon dioxide is
only about 0.04 per cent of the atmosphere, it is a very important
greenhouse gas because it absorbs infrared well.
The Sun’s rays enter the Earth’s
atmosphere
Heat is emitted back from the
Earth’s surface at a lower
principal frequency than that
emitted by the Sun
Some heat passes back out into
space
But some heat is absorbed by
carbon dioxide, a greenhouse
gas, and becomes trapped
within the Earth’s atmosphere.
The Earth becomes hotter as a
Greenhouse effect
Water vapour and methane
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Water vapour and methane
Other greenhouse gases are water vapour,
and also methane. Even though methane is
present in trace (tiny) amounts only, it is a
very efficient absorber of infrared.
The carbon cycle
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The carbon cycle
The amount of carbon dioxide in the atmosphere is controlled by
the carbon cycle.
Processes that remove carbon dioxide from the air:
photosynthesis by plants
dissolving in the oceans.
Processes that return carbon dioxide from the air:
respiration by plants, animals and microbes
combustion ie burning wood and fossil fuels such as coal, oil and
gas
thermal decomposition of limestone, for example, in the
manufacture of iron, steel and cement.
MORE
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Cellulose
All cells contain carbon, because they all contain
proteins, fats and carbohydrates. For example, plant
cell walls are made of cellulose, a carbohydrate.
Decomposers
Decomposers, such as microbes and fungi, play an
important role in the carbon cycle. They break down
the remains of dead plants and animals and, in
doing so, release carbon dioxide through
respiration.
Diagrams
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For thousands of years, the processes in the carbon
cycle were constant, so the percentage of carbon
dioxide in the atmosphere did not change. Over the
past 200 years, the percentage of carbon dioxide in
the atmosphere has increased steadily because
humans are:
burning more and more fossil fuels as energy
sources
burning large areas of forests to clear land, which
means that there is less photosynthesis removing
carbon dioxide from the air.
Global warming
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Global warming
Although the changes have been gradual, most - but not all - scientists
agree that the climate is getting gradually warmer. This is called global
warming.
Most - but not all - scientists lay the blame for this on human activities
increasing the amount of carbon dioxide in the atmosphere.
Global warming could cause:
climate change
extreme weather conditions in some areas.
Climate change may make it impossible to grow certain food crops in some
regions. Melting polar ice, and the thermal expansion of sea water, could
cause rising sea levels and the flooding of low-lying land. Extreme weather
events become more likely due to increased convection accompanied by
more water vapour being present in the hotter atmosphere.
Computer climate models - Higher tier
One piece of evidence that supports the view of scientists who blame
human activities for global warming has been provided by 'supercomputers'.
Computer generated climate models, based on different amounts of carbon
dioxide in the atmosphere, produce the same changes as have been
observed in the real world.
Ideas about science – correlation
and cause
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Ideas about science – correlation and cause
The ideas of correlation and cause are illustrated with the evidence
for global warming.
Any process can be thought of in terms of factors that may affect
an outcome.
in global warming, one factor is the amount of carbon dioxide in the
atmosphere. The outcome is the mean temperature of the atmosphere.
Establishing a correlation
To establish a correlation between a factor and an outcome,
convincingevidence is needed. This usually means that enough data
must be collected, and that different samples should match.
Compare these two graphs and consider these questions:
are the changes reported significantly large?
are they properly matched in terms of the times over which they are
reported?
do these two graphs match well enough? P.T.O
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Other factors
A correlation between a factor and an outcome does not mean that the factor
causes the outcome. They could both be caused by some other factor.
For emample: Children with bigger feet (factor) are, on average, better readers
(outcome).
There is another factor which affects both of these things: age. Older children
usually have bigger feet, and older children are usually better readers!
To investigate the relationship between a factor and an outcome, it is important
to control all other factors that may affect the outcome.
Other factors affecting global warming
Another factor that may affect the mean temperature of the atmosphere is the
amount of energy given out by the Sun. Most scientists agree that this has not
changed in the past 200 years
There are some scientists who agree that global warming is taking place, but do
not agree that carbon dioxide levels are to blame.
Scientific explanation - Higher tier
Once experiments have shown that there is a definite correlation between a
factor and an outcome, it is still not enough to prove that the factor causes the
outcome.
For this to be proven, there must be some scientific explanation of how the
relationship can happen.
for carbon dioxide and global warming, the explanation is that carbon dioxide is
a greenhouse gas. It absorbs infrared given off by the warm Earth, and this
infrared cannot then escape into space. This keeps the Earth warmer than it
would be if the carbon dioxide did not absorb so much infrared.
Waves and communication
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Information such as computer data can be transmitted in a number
of ways, including via waves and also analogue and digital
signals. Some methods of transmission have advantages over
others.
Transmitting information
Infrared light, microwaves and radio waves are all used to transmit
information such as computer data, telephone calls and TV signals.
Infrared light
Information such as computer data and telephone calls can be
converted into infrared signals and transmitted by optical fibres.
Optical fibres are able to carry more information than an ordinary cable
of the same thickness. In addition the signals they carry do not weaken
so much over long distances. Television remote controls use infrared
light to transmit coded signals to the television set in order to, for
example, change channels or adjust the volume.
Microwaves
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Microwave radiation can be used to transmit
signals such as mobile phone calls.
Microwave transmitters and receivers on
buildings and masts communicate with the
mobile telephones which are in their range.
Certain microwave radiation wavelengths
pass through the Earth’s atmosphere and can
be used to transmit information to and from
satellites in orbit.
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Radio waves
Radio waves are used to transmit television
and radio programmes. Longer wavelength
radio waves are reflected from an electrically
charged layer of the upper atmosphere. This
means they can reach receivers that are not
in the line of sight because of the curvature of
the Earth’s surface.
Carrying analogue and digital
information
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Carrying analogue and digital information
Analogue and digital
Before a sound or piece of information is transmitted, it
is encoded in the transmitter in one of the ways described below
- analogue or digital. The receiver must then decode the signal to
produce a copy of the original information or sound.
Analogue signals vary continuously in amplitude, frequency or
both.
Digital signals are a series of pulses with two states - on (shown
by the symbol ‘1’) or off (shown by the symbol ‘0’). Digital signals
carry more information per second than analogue signals and
they maintain their quality better over long distances.
You should be able to explain why digital signals maintain
their quality better than analogue signals.
Noise
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Noise
All signals become weaker as they travel long
distances. They may also pick up random extra
signals. This is called noise, and it is heard as
crackles and hiss on radio programmes. Noise may
also cause an internet connection to drop, or slow
down as the modem tries to compensate.
An important advantage of digital signals over
analogue signals is that if the original signal has
been affected by noise it can be recovered more
easily. In analogue signals, when the signal is
amplified to return to its original height, noise gets
amplified as well.
Analogue vs. digital - Higher tier
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Analogue vs. digital - Higher tier
Analogue signals
Noise adds extra random information to analogue signals. Each time
the signal is amplified the noise is also amplified. Gradually, the
signal becomes less and less like the original signal. Eventually, it
may be impossible to make out the music in a radio broadcast from
the background noise, for example.
Digital signals
Noise also adds extra random information to digital signals.
However, this noise is usually lower in amplitude than the 'on' states
of the digital signal. As a result, the electronics in the amplifiers can
ignore the noise and it does not get passed along. This means that
the quality of the signal is maintained. This is one reason why
television and radio broadcasters are gradually changing from
analogue to digital transmissions. They can also squeeze in more
programmes because digital signals can carry more information per
second than analogue signals. Another advantage of digital signals
is that information can be stored and processed by computers.
Coding and storing information
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Coding
Coding involves converting information from one form to another. All
types of information can be coded into a digital signal.
Digital signals are a series of pulses consisting of just two
states, ON (1) or OFF (0). There are no values in between. The
sound is converted into a digital code of 0s and 1s, and this coded
information controls the short bursts of waves produced by a source.
When waves are received, the pulses are decoded to produce a
copy of the original sound or image.
Amount of information
The amount of information needed to store an image or sound is
measured in bytes (B).
A megabyte is larger than a byte, and a gigabyte is larger than a
megabyte.
To store one minute’s worth of music it would take about 1
megabyte, to store an average two hour movie it would take 1.5
gigabytes.
In general, the more information that is stored about an image or
sound, the higher the quality.
P3 – SUSTAINABLE ENERGY
INCLUDING:
Using energy
Generating electricity
Choosing energy sources
Using energy
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The world we live in uses a lot of energy. There are a
number of different energy sources that could be used.
The energy supplied in household electricity is measured
in kilowatt hours (kWh). Energy is transferred from the
power source to components in an electric circuit.
Energy transfer in electrical appliances is always less
than 100 per cent efficient.
Energy sources
The global demand for energy is continually increasing. Our
population is growing even though we already have more
people on the planet than ever before.
As well as this, modern lifestyles demand transport and
communications technology, which also require more energy.
This raises issues about the availability of energy sources and
the environmental effects of using them.
Primary and secondary sources
A primary source of energy is one that occurs
naturally.
 Fossil fuels (coal, oil and gas), biofuels, wind,
waves, solar radiation and nuclear fuels are
all primary sources of energy.
 A secondary energy source is one that is
made using a primary resource. Electricity is
secondary resource, and can be generated
by a number of different primary sources.
Fossil fuels
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Fossil fuels
Fossil fuels are formed over millions of years
by the decay of dead organisms. When they
are burned they produce a number of
pollutants. A major pollutant formed
is carbon dioxide, which contributes to
global warming and climate change.
Power
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Power
When an electric current flows in a circuit, energy is transferred from
the power supply to the components in the circuit. The bigger the
voltage, the more energy transferred.
Energy is measured in joules, J.
The rate of energy transfer is called the power.
Power is measured in watts, W.
The equation
The equation below shows the relationship between power (watt, W),
voltage (volt, V) and current (ampere, A).
power = voltage x current
If the voltage is 12V and the current is 5A, the power is 12 x 5 = 60W.
This means that 60J of energy is transferred per second. (1 watt = 1
joule per second).
Remember that 1,000W is 1kW (kilowatt).
Energy Transfer
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You should be able to calculate the cost of using an electrical
appliance when given enough information about it.
The unit: kilowatt-hours, kWh
The amount of electrical energy transferred to an appliance depends
on its power and the length of time it is switched on. The amount of
mains electrical energy transferred is measured in kilowatt-hours,
kWh. One unit is 1kWh.
The equation below shows the relationship between energy
transferred, power and time:
energy transfered (kilowatt-hour, kWh) = power (kilowatt, kW)
x time (hour, h)
Note that power is measured in kilowatts here, instead of the more
usual watts. To convert from W to kW you must divide by 1000. For
example, 2000W = 2000 ÷ 1000 = 2kW.
Also note that time is measured in hours here, instead of the more
usual seconds. To convert from seconds to hours you must divide
by 3600 (this is the number of seconds in 1 hour). For example,
1800s = 0.5 hours (1800 ÷ 3600)
The cost of electricity
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The cost of electricity
Electricity meters measure the number of units of
electricity used in a home or other building. Units
(kilowatt-hours) are used instead of joules
because a joule is too small a unit of energy.
The more units used, the greater the cost. The
cost of the electricity used is calculated using this
equation:
total cost = number of units x cost per unit
For example, if 5 units of electricity are used at a
cost of 8p per unit, the total cost will be 5 × 8 =
40p.
Efficiency of energy transfer
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'Wasted' energy
Energy cannot be created or destroyed. It can only be
transferred from one form to another, or moved. Energy
that is "wasted", like the heat energy from an electric lamp,
does not disappear. Instead, it is transferred to its
surroundings and spreads out so much that it becomes
difficult to do anything useful with it.
Electric lamps
Ordinary electric lamps contain a thin metal filament that
glows when electricity passes through it. However, most of
the electrical energy is transferred as heat rather than light
energy. This is the Sankey diagram for a typical filament
lamp.
Modern energy-saving lamps work
in a different way. They transfer a
greater proportion of electrical
energy as light energy. This is the
Sankey diagram for a
typical energy-saving lamp.
Sankey diagram for a typical
energy-saving lamp
From the diagram, you can see
that much less electrical energy
is transferred or 'wasted' as heat
energy when using an energysaving lamp.
Calculating efficiency
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Calculating efficiency
The efficiency of a device such as a lamp can be calculated
using this equation:
efficiency = (useful energy transferred ÷ energy
supplied) × 100
The efficiency of the filament lamp is 10 ÷ 100 × 100 =
10%. This means that 10% of the electrical energy supplied
is transferred as light energy. 90% is transferred as heat
energy.
The efficiency of the energy-saving lamp is 75 ÷ 100 × 100
= 75%. This means that 75% of the electrical energy
supplied is transferred as light energy. 25% is transferred
as heat energy.
Note that the efficiency of a device will always be less
than 100%.
Efficiency of power stations
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The energy produced by burning fuel is
transferred as heat and stored in water
as steam. The energy in steam is transferred
to movement in a turbine, then to electrical
energy in the turbine. Energy is lost to the
environment at each stage. Here is a Sankey
diagram to show these losses:
Note that only about a
third of the energy
stored in the fuel was
transferred as
electrical energy to
customers.
Generating electricity
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Electricity is a convenient source of
energy and can be generated in a number
of different ways. You will need to weigh
up the advantages and disadvantages of
other ways of producing energy, such as
the use of nuclear power stations.
Electricity
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Electricity
Coal, oil and natural gas are primary energy
sources. Electricity is a secondary energy source
because we use primary energy sources to produce
it. These primary sources can be non-renewable or
renewable. Electricity itself is neither non-renewable
nor renewable.
Electricity is convenient because:
it is transmitted easily over distance, through
electricity cables
it can be used in many ways, for example electric
lamps, heaters, motors etc
Generating electricity
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Generators are the devices that transfer kinetic energy into
electrical energy. Mains electricity is produced by generators.
Turning generators directly
Generators can be turned directly, for example by:
wind turbines
hydroelectric turbines
wave and tidal turbines
When electricity is generated using wave, wind, tidal or
hydroelectric power (HEP) there are two steps:
The turbine turns a generator.
Electricity is produced.
Turning generators indirectly
Generators can be turned indirectly using fossil or nuclear fuels.
The heat from the fuel boils water to make steam, which expands
and pushes against the blades of a turbine. The spinning turbine
then turns the generator.
These are the steps by which electricity is generated from
fossil fuels:
Heat is released from a primary energy source fuel and boils
the water to make steam .
The steam turns the turbine.
The turbine turns a generator and electricity is produced.
The electricity goes to the transformers to produce the
correct voltage.
Generating a current
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Generating a current
Generators work using a process
called electromagnetic induction.
One way of generating a current is to move a
magnet into or out of a coil. This movement
causes a voltage to be induced across the
ends of the coil. If the coil is part of a
complete circuit then a current will be
induced in the circuit.
On magnet in
the magnet
goes in and
the dial turns
to the + sign
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If this is done over and over again, an alternating
current (a.c.) is generated. An alternating current is
an electric current that reverses direction many
times a second.
It is not practical to generate large amounts of
electricity by passing a magnet in and out of a coil of
wire. Instead, generators induce a current by
spinning a coil of wire inside a magnetic field, or
by spinning a magnet inside a coil of wire.
Some bicycles use a small generator. It uses the
movement of the wheel to produce a current.
Nuclear power stations
Nuclear power stations use fuel
containing uranium.
These are the steps by which
electricity is generated by
nuclear power:
Uranium atoms split releasing
energy so fuel becomes hot.
This heats the water turning
it into steam.
The steam turns the turbine.
The turbine turns a generator
and electricity is produced.
The electricity goes to the
transformers to produce the
correct voltage.
The fuel used eventually
becomes solid nuclear
waste. This waste is
radioactive and emits
ionising radiation.
Ionising radiation and living cells
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The radiations from radioactive materials –
alpha, beta and gamma radiation – are all ionising
radiations which can damage living cells.
This happens because ionising radiation can break
molecules into bits called ions. These ions can then
take part in other chemical reactions in the living
cells.
This may result in the living cells dying, or
becoming cancerous.
Radiation warning symbol
Hazards from radioactive materials
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Hazards from radioactive materials
Radioactive materials in the environment, whether
natural or artificial, expose people to risks.
This can happen in two ways:
The radiation from the material can damage the
cells of the person directly. This is damage
by irradiation.
Some of the radioactive material can be swallowed
or breathed in. While inside the body, the radiation it
emits can cause damage. This is damage
bycontamination.
Ideas about science - risk
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Ideas about science - risk
Scientific or technological developments often introduce new risks:
The development of radioactive materials in the early 20th century led
to the deaths of many workers. As the materials were new, no one
realised they could be dangerous.
Risk can sometimes be assessed by measuring its chance of occurring
in a large sample:
The safe dose that people may receive has been based on the rate of
cancer in workers exposed to radiation over many years.
It is important to be able to assess the size of risks in any activity. No
activity is completely safe:
The likelihood of dying from a nuclear accident has been calculated,
and it is very low. Cycling is much more dangerous.
For most risky activities, there are benefits as well as risks:
A gamma scan gives doctors valuable information to help cure a
patient. This benefit outweighs the slight risk from the gamma radiation
itself.
Making a judgement - higher tier
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To make a judgement about a possible bad outcome you need to
consider two factors:
What is the chance of the outcome happening?
 If the radiation dose someone has received is known, the chance
of them getting a cancer is also known.
What is the consequence of that outcome?
 Cancers are serious conditions but, if diagnosed early, treatment
is now very successful for most types. This makes the
consequence less severe.
The idea is that you may decide to avoid any activity if serious
harm could arise. For example, people who are worried about
working with radioactive materials may turn down a job in any
situation where radioactive materials are used.
Perceived and real risk
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The real risk may be very different from the perceived risk ie
the risk that you think is there.
Nuclear radiation is invisible, and sounds threatening to many
people. This makes the risk seem worse than something you can
see, and which is more familiar.
Many people do not realise that nuclear radiation has always
been part of our environment.
People are afraid that irradiated food is itself radioactive, even
though this is not true.
Sometimes risk should be regulated by governments and other
public bodies. This usually applies to an organisation that is
responsible for its employees. In some situations decisions my
be made by the organisation or public body that may cause
controversy.
National Grid
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There are issues around the distribution of electricity
through the country as well as with the generation of
it.
The electricity we use in our homes is distributed
through the National Grid. All power stations are
connected to the National Grid, who own and
maintain the high-voltage electricity distribution
through the UK.
Often electricity is needed far from where the power
station is. As the current flows along wires to where
it is needed, it heats the wires meaning energy is
lost.
Reducing energy losses
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To reduce the energy lost when distributing
electricity, a high voltage is used. The mains
supply voltage in our homes is 230 volts.
Large currents would be needed to distribute
electricity at 230 volts. This would heat wires
and so the loss of energy would be large.
So, the National Grid distributes electricity at
a much higher voltage. This means a lower
current is needed and so less energy is lost
due to heating.
Choosing energy sources
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A number of different energy sources
exist. Some of these are renewable and
some are not. All of us have difficult
choices to make when using energy,
though it is clear that a mix of sources will
need to be used.
Different kinds of energy sources p.t.o
Renewable energy sources
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Our renewable energy resources will never run out.
Their supply is not limited. There are no fuel costs
either. And they typically generate far less pollution
than fossil fuels.
Renewable energy resources include:
wind energy
water energy, such as wave machines, tidal
barrages and hydroelectric power
geothermal energy
solar energy
biomass energy, for example energy released from
wood
However, there are some
negatives to generating
renewable energy. For
example, wind farms are noisy
and may spoil the view of
people who live near them.
The amount of electricity
generated depends on the
strength of the wind. Also, if
there is no wind, there is no
electricity.
Non-renewable energy sources
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There is a limited supply of non-renewable energy resources,
which will eventually run out. They include:
fossil fuels, such as coal, oil and natural gas
nuclear fuels, such as uranium
Fossil fuels release carbon dioxide when they burn, which
adds to the greenhouse effect and increases global
warming. Of the three fossil fuels, coal produces the most
carbon dioxide, for a given amount of energy released, while
natural gas generates the least.
The fuel for nuclear power stations is relatively cheap. But the
power stations themselves are expensive to build. It is also
very expensive to dismantle old nuclear power stations or
store radioactive waste, which is a dangerous health hazard.
Nuclear power stations
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The main nuclear fuels are uranium and plutonium, both of
which are radioactive metals. Nuclear fuels are not burned to
release energy. Instead, heat is released from changes in
the nucleus.
Just as with power stations burning fossil fuels, the heat
energy is used to boil water. The kinetic energy in the
expanding steam spins turbines, which drive generators to
produce electricity.
Advantages
Unlike fossil fuels, nuclear fuels do not produce carbon
dioxide.
Disadvantages
Like fossil fuels, nuclear fuels are non-renewable energy
resources. And if there is an accident, large amounts of
radioactive material could be released into the environment.
In addition, nuclear waste remains radioactive and is
hazardous to health for thousands of years. It must be stored
safely.
Evaluating energy sources
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When evaluating energy sources you must consider:
where the energy source is used (at home, in the work place or
at a national level)
factors that affect the choice of energy source (economics,
environmental impact, waste produced including carbon dioxide)
the advantages and disadvantages of the energy source
All of us have choices to make on the use of energy. Some
would argue that we should not use less energy so we can
maintain a good standard of living. Others would argue that
reducing the amount of energy we use is essential.
There are a numbers of steps that could be taken to address
problems faced by the energy industry. An important point we
know for sure is that we need a mix of energy sources to meet
the United Kingdom’s energy demands
Ideas about science - making decisions
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Scientific applications give people things that they value, but may have
undesirable impacts on the environment.
Our society uses more and more energy every year, but the carbon dioxide
produced by most power stations is believed to be causing serious damage to
the climate.
Natural resources should be used in a sustainable way.
The use of renewable energy sources would guarantee energy for the future. At
the moment, renewable energy sources cannot provide enough energy.
There are official regulations and laws which control scientific research and
applications.
The nuclear industry is regularly inspected to ensure that standards of safety are
maintained.
Some applications of science have ethical implications. One point of view is that
the right decision is the one which gives the best outcome for most people.
Another point of view is that certain actions are never justified because they are
wrong.
Disposal of nuclear waste raises ethical problems:
Some people say that we must have nuclear power, or we will not be able to
combat global warming and still produce enough energy.
Others say that it is unethical to produce waste that will still be dangerous in
many thousands of years’ time.
Weighing up the arguments - higher tier
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Before deciding on a course of action, it is important to ask if it
is feasible. Can it be done? Then it is possible to consider if it ought to
done.
If nuclear waste could be sent down into the Earth’s mantle, it would
take millions of years to resurface. Unfortunately, there doesn’t seem to
be any way to do this. It is not feasible.
Nuclear waste could be sent into space in rockets so that it falls
harmlessly into the Sun. Unfortunately, this would be far too expensive,
and any accident on take-off would spread dangerous waste over a
large area. It ought not to be done.
In different social and economic contexts, different decisions might be
taken.
Many developing countries insist that they need to burn fossil fuels in
their power stations, even if it produces global warming. They need this
to allow them to catch up with the standard of living that we enjoy.
END OF P1,P2,P3
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This covers the basis of the needed revision.
Teaching and learning this will help you
achieve A*/A
Careful learning will make everything on the
exam paper to your level of ability.
This PowerPoint is for OCR 21ST CENTURY
PHYSICS P1,P2,P3