OCR 21OCR 21stst Century Century Science Science

Unit P1a Revision Unit P1a Revision The earth in the universe

19/04/23The eight planets of our Solar The eight planets of our Solar SystemSystem

Mercury

MarsJupiter

Saturn

Neptune

Uranus

VenusEarth

As well as the eight planets, the solar system is also made up of asteroids, dwarf planets, comets and

moons

19/04/23Different OrbitsDifferent Orbits

Mercury

MarsJupiter

Saturn

Neptune

Uranus

Pluto

VenusEarth

Mercury = 88 days

Mars = 687 days

Pluto = 90,500 days

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AsteroidsAsteroids

An “asteroid belt” lies between Mars and Jupiter. But what is an asteroid?

19/04/23CometsCometsComets are balls of dust and frozen gas. They have very elliptical orbits:

Notice how the tail always points away from the sun!

19/04/23The Solar System The Solar System summarisedsummarisedWhat makes up our solar system? Complete the following

mind map with what you now about each object:

The solar system

19/04/23Solar systems, galaxies and the Solar systems, galaxies and the UniverseUniverse

OUR SUN (100 times wider and 4.6 billion years old), which is small compared to…

THE MILKY WAY, which contains at least 200 billion stars and is 100,000 light years across, which is small compared to…

Our planet (around 13,000km diameter and 4500 million years old) is pretty small compared to...

THE UNIVERSE, which contains billions of galaxies and is 14,000 million years old.

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How to make a solar systemHow to make a solar system

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………

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Stage 1: NebulaeStage 1: Nebulae

A nebulae is a collection of dust, gas and rock.

Some examples of nebulae…

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Gravity will slowly pull these particles together…

As they move inwards their gravitational potential energy is converted into heat and a big object (PROTOSTAR) or smaller objects (planets, asteroids etc) are formed

Stage 2: Throw the nebula Stage 2: Throw the nebula togethertogether

19/04/23Stage 3: Make a starStage 3: Make a star

Any element in space that is heavier than helium is thought to have been made in a star.

In a star the forces of gravitational 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 combining hydrogen and helium nuclei (light elements) into _________ elements.

Words – heavier, balanced, hydrogen, nuclear, temperatures

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Observing the UniverseObserving the Universe

All of these methods rely on detecting radiation from stars.

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The Light YearThe Light Year

Distances in space are so big that they are measured in units called “light years”:

1 light year = the distance travelled by light

in one yar

Q. If light travels through space (i.e. A vacuum) at 300,000 km/s how far is one light year?

Because of this, when we see stars in the night sky we are actually seeing them as they were in the past.

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Distances in spaceDistances in space19/04/23

The Sun, our closest star, is 1.6x10-5 light years away from us.

The Andromeda Galaxy (our closest galaxy) – approximately 2.5 million light years away

The next closest star, Proxima Centauri (4.2 light years away)

The centre of our galaxy, the Milky Way, is around 26,000 light years away.

19/04/23Measuring distance using Measuring distance using brightnessbrightness

When I look at these stars some appear brighter than others. This because they are either brighter stars or closer to me.For example, the star Antares is 10,000 times brighter than the sun but it is 500 light years away from me, so it is only the 15th brightest star in the night sky.

19/04/23Measuring distances to Measuring distances to starsstars

Distant stars

Nearby star

1) Relative BrightnessThe further away a star is the dimmer it is. Simple.

2) Parallax

Parallax is the apparent change in position of closer stars due to the Earth moving around the sun.

19/04/23Problems in Measuring Problems in Measuring DistancesDistances

1) Light pollution and other atmospheric conditions can interfere with observing stars:

2) Stars are simply very far away so the angles involved in using techniques like parallax are very small:

19/04/23How our Earth and the Sun How our Earth and the Sun compare to others… compare to others…

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19/04/23How did the universe How did the universe begin?begin?

Scientists believe that the universe began by a “big bang” around 14 billion years ago:

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Evidence about the Evidence about the origins of the universe…origins of the universe…

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Source of light “Spectra

”

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If you pass the light through a gas something different is seen…

helium

Some wavelengths of light are absorbed by

the gas – an “absorption spectrum”.

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After

helium

If the light source is moving away the absorption spectra look a little different…

helium

Before

19/04/23The absorption lines have all been “shifted” towards the longer wavelength end (red end)…

After

Before

A similar effect happens with sound – this is called “The

Doppler Effect”

This is called red shift. The faster the light source moves the further its light will be “shifted”

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Red Shift simplifiedRed Shift simplified

Basically, if I walk towards you I’ll look slightly more blue. Then, if I

walk away from you, I’ll look slightly more red!!

Let’s try it…

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Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point.

This is the BIG BANG theory

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Red shift summaryRed shift summaryLight 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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Hubble’s LawHubble’s Law

Edwin Hubble

1889-1953

The speed at which galaxies are moving away from us is

proportional to their distance from us.

In other words, the further away they are, the faster they go.

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Big Bang TheoryBig Bang Theory19/04/23

Some scientists have explained that red shift can actually be used to support the Big Bang Theory – this explanation is based around the rates of expansion and contraction of different galaxies. If our neighbouring galaxy is expanding at a different rate to the Milky Way then it will appear red or blue-shifted.

Stephen Hawking, 1942 -

So Mr President, red shift shows us that galaxies are moving and therefore we assume that space itself is expanding. Elementary!

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The end of the UniverseThe end of the Universe

There are some theories about how the universe will end but its difficult to tell due to difficulties in measuring objects

that are so far away:

“The big crunch” – if there is too much mass (i.e. too much matter) the universe will collapse under its own gravity. It may then do another “big bang” – this is the “oscillating universe” theory.

“Expanding Universe” – if there isn’t enough mass in the universe then it will just keep on expending forever.

If there is just the right mass in the universe then it will reach a fixed size.

19/04/23

The End of the UniverseThe End of the Universe

Stephen Hawking

Basically, how the universe will end depends on its “energy-mass

density”.

Siz

e o

f u

niv

ers

e

Time

Open universe

Closed universe

Critical density

Now

OCR 21OCR 21stst Century Century Science Science

Unit P1b Revision Unit P1b Revision The changing earth

19/04/23Evidence for the age of the Evidence for the age of the EarthEarth

Scientists once thought that the Earth was only 6000 years old. Rocks have provided lots of evidence for the world being older.

1) Erosion

2) Craters

3) Mountains

4) Fossils

5) Folding

6) Radioactive dating

The Earth’s age must be older than the oldest rocks, which are around 4,000,000,000 years old.

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Continental DriftContinental DriftLook at the coastlines of South America and Africa. I wonder of

they used to fit together…

Alfred Wegener

I’m going to call this my Theory of Continental Drift

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Tectonic theoryTectonic theory

What’s my evidence for this? Three things:

1) The “jigsaw fit”

2) Each continent has similar rocks and fossils

3) Each continent has similar animal species

19/04/23Another Example of Continental Another Example of Continental DriftDrift

The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India:

This is where India is now

This is where India was

millions of years ago

If it wasn’t for processes like this then, if you think about it, continents would eventually disappear due to erosion. Fascinating.

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Tectonic theoryTectonic theoryThe Evidence:

1) Some continents look like they used to “fit” together

2) Similar rock patterns and fossil records

The Problems:

Wegener couldn't explain how continental drift happened or provide evidence so nobody believed him. Also, he wasn’t a geologist so he had no credibility and there were other explanations for the same evidence.

Conclusion – scientists now believe Wegener’s Tectonic Theory

The Answer:

Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move.

19/04/23Movement of the Movement of the LithosphereLithosphereThe Earth’s LITHOSPHERE (i.e. the _______) is split up

into different sections called ________ plates:

These plates are moving ______ from each other a few centimetres every _______. They can slide past each other, move apart from each other or move towards each other, causing volcanoes and _________.Words – earthquakes, crust, apart, tectonic, year

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Sea Floor SpreadingSea Floor Spreading

Oceanic Crust

Mantle

Magma

Earthquakes and volcanic eruptions can be common here

Igneous Rock

Convection Currents

19/04/23Magnetic Patterns in Sea Floor Magnetic Patterns in Sea Floor SpreadingSpreading

The Earth’s magnetic field swaps poles every million years. The above picture shows those changes recorded over time in rocks on the sea floor and provides evidence for long-term sea floor spreading.

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More on Plate MovementsMore on Plate Movements

Convection Currents

Thin, dense oceanic plate

Thick, less dense

continental plate

Subduction

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The Structure of the EarthThe Structure of the EarthA thin crust - 10-100km thick and not very dense

A mantle – extends almost halfway to the centre, hot and dense

A core – made of molten nickel and iron. Outer part is liquid and inner part is solid. Gets hot due to radioactive decay.

How do we know? A lot of the evidence for these facts comes from studying earthquakes (seismic

waves)…

19/04/2319/04/23An introduction to WavesAn introduction to Waves

A Wave is a “movement of energy” but NOT a transfer of matter

19/04/2319/04/23Transverse vs. longitudinal Transverse vs. longitudinal waveswaves

Transverse waves are when the displacement is at right angles to the direction of the wave.

Longitudinal waves are when the displacement is parallel to the direction of the wave…

Dis

pla

cem

en

t

Direction

Direction

Displacement

Examples – light, other EM waves, some seismic waves

Examples – sound, some seismic waves

19/04/2319/04/23Seismic wavesSeismic wavesEarthquakes travel as waves through the Earth – we call them SEISMIC WAVES. There are two types:

P waves:1) They are longitudinal so they cause the

ground to move up and down

2) They can pass through solids and liquids

3) They go faster through more dense material

S waves:1) They are transverse so they cause the

ground to move from right to left

2) They ONLY pass through solids

3) They are slower than P waves

4) They go faster through more dense material

19/04/2319/04/23Seismic wavesSeismic waves

These P waves travel through the Earth and are refracted when they pass through a medium

These P waves are being reflected at the crust

These S waves cannot travel through the outer core as they only go through solids – this tells us that the outer core is liquid

The paths of these waves are all curved because density is

gradually changing

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Locating EarthquakesLocating Earthquakes

By measuring the time it takes the wave to travel to these locations the location of the earthquake can be found.

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Wave definitions…Wave definitions…

1) Amplitude – this is “how high” the wave is:

2) Wavelength () – this is the distance between two corresponding points on the wave and is measured in metres:

3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz)

4) Speed – this is how fast the wave travels and is measured in metres per second (m/s)

19/04/2319/04/23Distance, Speed Distance, Speed and Time for and Time for

waveswavesSpeed = distance (in metres)

time (in seconds)

D

TS

1) A water wave travels 200 metres in 40 seconds. What is its speed?

2) Another wave covers 2km in 1,000 seconds. What is its speed?

3) Sound travels at around 330m/s. How long does it take to travel one mile (roughly 1,600m)?

4) Light travels at a speed of 300,000,000m/s. How long would it take to travel around the world if the diameter at the equator is around 40,000km?

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Drawing wavesDrawing waves

1) Low amplitude, low frequency:

2) Low amplitude, high frequency:

3) High amplitude, low frequency:

4) High amplitude, high frequency:

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The Wave EquationThe Wave Equation

All E-M waves obey the Wave Equation:

Wave speed (v) = frequency (f) x wavelength ()

in m/s in Hz in m

V

f

Notice that frequency is inversely proportional to

wavelength – if wavelength goes up, frequency goes

down

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1) A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving?

2) A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves?

3) The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound?

4) Purple light has a wavelength of around 6x10-7m and a frequency of 5x1014Hz. What is the speed of purple light?

Some example wave equation Some example wave equation questionsquestions

0.2m

0.5m

0.6m/s

3x108m/s

OCR 21OCR 21stst Century Century Science Science

Unit P2a Revision Unit P2a Revision Electromagnetic radiation

19/04/23

Radiation – the basicsRadiation – the basics

Wow it’s hot here!

I’m not so bad thanks

When radiation hits a surface it is usually either absorbed, reflected or transmitted, or a combination

of these things.

Lots of objects (“sources”) emit radiation. For example, consider the sun. The sun, amongst others, emits light and heat:

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LightLight

White light is a mixture of colours:

RED LIGHT is made of “low energy

photons”

PURPLE LIGHT is made of “high energy

photons”

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19/04/23The Electromagnetic The Electromagnetic SpectrumSpectrum

Gamma rays

X-rays Ultra violet Visible light

Infra red Microwaves

Radio/TV

Each type of radiation shown in the electromagnetic spectrum has a different wavelength and a different frequency:

Each of these types travels at the same speed through a _______ (300,000km/s), and different wavelengths are absorbed by different surfaces (e.g. infra red is absorbed very well by ___________ surfaces). This absorption may heat the material up (like infra red and _______) or cause an alternating current (like in a __ _______).

Words – black, microwaves, low, high, TV aerial, vacuum

High frequency, ____ energy

Low frequency, ________ energy

γ

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PhotonsPhotonsLight (and the other types of EM radiation) travel in “packets” called photons:

Here comes a photon…

And another…

And another…

Higher frequency radiation (i.e. gamma and x rays) consist of

photons of higher energy.

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Intensity of light and heatIntensity of light and heat

The heat here is very intense!

The heat here isn’t so bad...

Why?

When a body absorbs radiation the amount of heat it gains depends on the intensity (power per square

metre per second) and the time of the exposure.

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An example questionAn example questionWhich of these surfaces would warm up the quickest when receiving infra red photons from the sun?

What factors are affecting the answer?

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IntensityIntensityClearly, the intensity of radiation received by an object decreases the further out the object is. This is due to two things:

1) The radiation “spreads out” in a circle

2) It is also absorbed by the medium it travels through

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IonisationIonisation

Radiation

Some types of radiation are dangerous because they “ionise” atoms – in other words, they change atoms by turning them into _____ by “knocking off” __________:

Ionisation causes chemical reactions which cause _____ in living tissue to mutate, usually causing _______. High doses can destroy cells completely, causing radiation sickness. This takes a lot of ______ so only high energy radiations like ________, x rays and ultra violet can do it.

Words – energy, gamma, electrons, ions, cancer, cells

19/04/23Recap on absorbing Recap on absorbing radiationradiationWho would warm up the quickest when receiving infra red

photons from the sun?

What would happen of either of these people absorbed too much heat?

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Dangers of Mobile PhonesDangers of Mobile PhonesMany people are concerned with the possible dangers of using mobile phones, especially for children.

Your task:

Find out about some of the research that has taken place in the last 20 years over the use of mobile phones, including:

1) Some evidence that using them is dangerous

2) Other evidence that it isn’t

3) Whether or not living near mobile phone masts is dangerous

4) How coming to an overall conclusion can be difficult

19/04/23How do Microwaves heat How do Microwaves heat food?food?

How does the design of a microwave oven protect the user from harm?

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19/04/23Introduction to Introduction to RadioactivityRadioactivity

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 gamma radiation – this is called “radioactive decay”. Increased exposure to gamma radiation can cause cancer or cell death.

19/04/23Warning the Public about UV Warning the Public about UV DangersDangers

Over the last few years the public has received many warnings about the dangers of ultraviolet radiation:

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OzoneOzone

Diagram showing the quantity of ozone in different parts of the southern hemisphere

Global production of CFCs over the last 60 years –

notice the change!

Ozone is a chemical (O3) in the atmosphere that absorbs harmful UV rays from the sun. This causes chemical reactions in the atmosphere. Unfortunately, it’s getting thinner:

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SuncreamSuncreamUltra violet radiation in sunshine can be dangerous and cause skin cancer, cataracts and premature skin aging.

It is recommended that you spend no more than 20 minutes in the sun on a sunny day. However, you could also use suncream:

Of course, wearing clothes always helps!

19/04/23Protection against harmful Protection against harmful radiationradiation

A lead screen protecting from x-rays

Containment structures around a nuclear reactor

Physical barriers can be used to absorb radiation, e.g.

The fact that x-rays are absorbed by hard substances makes them very useful:

OCR 21OCR 21stst Century Century Science Science

Unit P2b Revision Unit P2b Revision EM radiation 2

19/04/23

Principal FrequencyPrincipal FrequencyAll objects emit radiation of some kind. The “principle frequency” of that radiation depends on the object’s temperature. For example, consider a Bunsen burner:

Blue is a higher frequency than yellow light – objects that are “blue hot” are often hotter than “yellow hot”

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The Greenhouse EffectThe Greenhouse EffectWe get heat from the sun:

A lot of this heat is _______ back into space.

However, most of it is kept inside the Earth by a layer of gases (e.g. carbon dioxide and ______) that prevent the heat escaping by _______ and then re-radiating it back again.

Words – methane, global warming, reflected, absorbing, frequency

The Earth reflects back radiation with a lower principal _______ that the radiation it receives from the sun. This radiation basically causes the earth to warm up – this is called “_______ ________” or the “Greenhouse Effect”.

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Global WarmingGlobal Warming

Facts:

1) The 10 warmest years of the last century have all occurred within the last 15 years

2) Sea level has risen by between 12 and 24cm in the last 100 years

3) Rainfall has risen by 1%

Carbon dioxide, methane and water vapour are all greenhouse gases but they are only present in small amounts. However, recently this balance has been getting “upset” causing this:

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Global Warming PredictionsGlobal Warming Predictions

Data taken from http://en.wikipedia.org/wiki/File:Global_Warming_Predictions.png

19/04/23The Effects of Global The Effects of Global WarmingWarmingThe following things could happen as a result of global warming:

1) Food – it will be impossible to grow crops in particular regions

2) More extreme weather conditions due to increased convection and larger amounts of water vapour

3) Flooding of low-lying land caused by ice caps melting and expansion of water

19/04/2319/04/23The Carbon The Carbon CycleCycle

CO2 in air 1. CO2 is taken

in by plants and algae for photosynthesis and turned into carbohydrates, fats and proteins

2. Plants and algae release CO2 through respiration

3. The carbon taken in by plants is then eaten by animals and the animals that eat them

4. Animals release CO2 through respiration

5. Burning fossil fuels also releases CO2

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The Carbon Dioxide BalanceThe Carbon Dioxide BalanceCarbon dioxide levels in the atmosphere have remained balanced due to the carbon cycle. However, over the last 200 years the level of CO2 in the atmosphere has risen due to activities like:

1) Deforestation, which takes away some of the trees that remove carbon dioxide

2) Burning fossil fuels, which releases more carbon into the atmosphere that was previously “locked up”

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Reflecting Radio wavesReflecting Radio waves

Some radio waves are refracted and then reflected off the atmosphere and suffer little absorption, which is useful as

they can travel further distances.

19/04/23Using Satellites with Using Satellites with microwavesmicrowaves

Microwaves are used to

communicate with satellites as they

are not absorbed by the atmosphere

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Analogue vs. DigitalAnalogue vs. DigitalAnalogue signals (like talking or music) continually vary in amplitude and/or frequency

+

-1

0

Digital signals, however, are either off or on, and the information is sent in a series of pulses

There are two main advantages of digital:

1) More channels can be sent down the same cable – “multiplexing”

2) Better quality, because a digital signal can be amplified without amplifying the extra noise:

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Transmitting informationTransmitting informationEM waves can also be used as “carrier waves” in order to send a signal:

Signal Carrier wave

Modulated wave Transmitter Wave is demodulated (“decoded”) back into a signal

Light signals can also be sent down optical fibres where they travel for long distances with little absorption:

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Using Light to send SignalsUsing Light to send Signals

Morse code is a signal that consists of short bursts and long bursts and therefore is classed as a “digital” signal as each message can be one of only two forms. These signals could be relayed between ships over long distances.

Modern signals can be sent by radio or electric signals instead. What are the advantages of these methods over using light?

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Storing Digital SignalsStoring Digital SignalsOne of the advantages of digital signals is that they can be stored and processed easily by computers.

Data is measured in units called “bytes”. 1 Byte = 8 bits, and is roughly the amount of data

needed to store one character of text.

Clearly, the large a file size, the more bytes it contains and therefore the higher quality the sound or image is.

OCR 21OCR 21stst Century Century Science Science

Unit P3a Revision Unit P3a Revision Sustainable energy

19/04/23

Energy ConsumptionEnergy Consumption

The demand for energy is predicted to rise by a large amount in the next few decades:

What issues will this rise in demand cause?

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FuelsFuelsA “fuel” is something that can be burned to release heat and light energy. The main examples are:

Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.

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Some definitions…Some definitions…A renewable energy source is clearly one that can be _______ (“renew = make again”), e.g. _____, solar power, biogas etc.

A ___________ energy source is one that when it has been used it is gone forever. The main examples are ____, oil and gas (which are called ______ ____, as they are made from fossils), and nuclear fuel, which is non-renewable but NOT a fossil fuel.

Electricity is called a “________ source” because it is converted from other forms – what would these forms be in batteries, wind turbines and solar panels?

Words – non-renewable, coal, fossil fuels, wood, renewed, secondary

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PollutionPollutionWhen a fuel is burned the two main waste products are _____ dioxide and ________ dioxide.

Carbon dioxide is a _________ ___ and helps cause _______ _________. This is produced when any fossil fuels are burned.

Sulphur dioxide, when dissolved in ________, causes ______ _____. This is mainly a problem for ___ power stations.

Nuclear power stations do not produce these pollutants because they don’t ____ fossil fuels.

Words – sulphur, coal, global warming, carbon, acid rain, greenhouse gas,

rainwater, burn

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Using ElectricityUsing ElectricityBasically, electrical devices are used to transfer electrical energy to the environment:

-+

This light bulb will transfer light and heat to the

surroundings.

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Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how much energy it uses every second.

In other words, 1 Watt = 1 Joule per second

E

TP

E = Energy (in joules)

P = Power (in watts)

T = Time (in seconds)

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Some example questionsSome example questions1) What is the power rating of a light bulb that transfers

120 joules of energy in 2 seconds?

2) What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?

3) Rob runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?

4) How much energy does a 150W light bulb transfer in a) one second, b) one minute?

5) Jonny’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a 50 minute physics lesson?

6) Lloyd’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?

60W

2KW

150J, 9KJ

120KJ

630MJ

0.2MW

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PowerPowerPower is “the rate of doing work”. The amount of power being used in an electrical circuit is given by:

P

IVPower = voltage x current

in W in V in A

We can use this equation to analyse power stations:

1) A transformer gives out 10A at a voltage of 50V. What is its power output?

2) An electric fire has a power rating of 2KW. If it runs on a voltage of 230V what is the current?

3) Electricity is transmitted along some lines in the National Grid at 400KV. If the current is 1KA what would be the power through the wire?

500W

8.7A

400MW

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The Cost of ElectricityThe Cost of ElectricityElectricity is measured in units called “kilowatt hours” (kWh). The kilowatt hour is a unit of energy but the Joule is too small to count so we use the KWh instead. For example…A 3kW fire left on for 1 hour uses 3kWh of energy

A 1kW toaster left on for 2 hours uses 2kWh

A 0.5kW hoover left on for 4 hours uses __kWh

A 200W TV left on for 5 hours uses __kWh

A 2kW kettle left on for 15 minutes uses __kWh

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The Cost of ElectricityThe Cost of ElectricityTo 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 8p per unit calculate the cost of the following…

1) A 2kW fire left on for 3 hours

2) A 0.2kW TV left on for 5 hours

3) A 0.1kW light bulb left on for 10 hours

4) A 0.5kW hoover left on for 1 hour

48p

8p

8p

4p

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Reading Electricity MetersReading Electricity Meters

1) How many units of electricity have been used?

2) If 1 unit costs 10p how much has this electricity cost?

1 month later…

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The 9 types of energyThe 9 types of energy

Type 3 example sources

Heat

Kinetic (movement)

Nuclear

Sound

Light

Chemical

Electrical

Gravitational potential

Elastic potential

Type 3 example sources

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The Laws of PhysicsThe Laws of PhysicsThere are many laws of physics, but one of the most important ones is:

Energy cannot be created or destroyed, it can only be

converted from one form to another

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Energy changesEnergy changesTo describe an energy change for a light bulb we need to do 3 steps:

Electricity Light + heat

1) Write down the starting energy:

3) Write down what energy types are given out:

2) Draw an arrow

What are the energy changes for the following…?

1) An electric fire

2) A rock about to drop

3) An arrow about to be fired

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Conservation of EnergyConservation of EnergyIn any energy change there is ALWAYS some “waste” energy:

e.g. a light bulb:

In this example HEAT is wasted and it is transferred to the surroundings, becoming very difficult to use.

Electricity Light + heat

Describe the following energy changes and state the “waste” energy or energies:

1) A vacuum cleaner

2) A TV

3) A dynamo/generator

19/04/23EfficiencyEfficiencyEfficiency 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)

Light (80J)

Sound (40J)

Heat (?)

Efficiency = Useful energy out

Energy in

x100%

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Some examples of efficiency…Some examples of efficiency…

1) 5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it?

2) A laptop can convert 400J of electrical energy into 240J of light and sound. What is its efficiency? Where does the rest of the energy go?

3) A steam engine is 50% efficient. If it delivers 20,000J of movement energy how much chemical energy was put into it?

0.2 or 20%

0.6 or 60%

40KJ

19/04/23Energy Transfer (“Sankey”) Energy Transfer (“Sankey”) diagramsdiagrams

Consider a light bulb. Let’s say that the bulb runs on 100 watts (100 joules per second) and transfers 20 joules per second into light and the rest into heat. Draw this as a diagram:

100 J/s electrical energy

“Input” energy “Output” energy

80 J/s heat energy (given to

the surroundings)

20 J/s light energy

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Example questionsExample questionsConsider a kettle:

1) Work out each energy value.

2) What is the kettle’s efficiency?

Sound energy

Wasted heat

Heat to water

2000 J/s electrical energy

Consider a computer:

150 J/s electrical energy

10 J/s wasted sound

20 J/s wasted heat

Useful light and sound

1) How much energy is converted into useful energy?

2) What is the computer’s efficiency?

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Reducing Energy UsageReducing Energy Usage

How can we reduceenergy usage?

OCR 21OCR 21stst Century Century Science Science

Unit P3b Revision Unit P3b Revision Generating energy

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Generators (dynamos)Generators (dynamos)Electricity is convenient because it can be transmitted over long distances and can be used in many ways. But how is it generated? We need to use a “generator”:

Basically, a generator works by spinning a magnet near a coil of wire. That’s useful, but how do we get this magnet to keep spinning?

19/04/23Using primary energy sources in power Using primary energy sources in power stationsstations

1) A fuel is burned in the boiler

2) Water turns to steam and the steam drives a turbine

3) The turbine turns a generator – if you want more electricity you have to burn more fossil fuels4) The output of the generator is connected to a transformer

5) The steam is cooled down in a cooling tower and reused

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Efficiency of Power StationsEfficiency of Power Stations

100J Boiler 85J Turbine35J

Generator30J

15J 50J 5J

Heat

Heat Kinetic

Heat Heat

Electrical

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Nuclear power stationsNuclear power stationsThese work in a similar way to normal power stations:

The main difference is that the nuclear fuel is NOT burnt. This means that they produce less pollution but they do produce radioactive waste

instead.

19/04/23Radioactive Waste - Radioactive Waste - IonisationIonisationRadiation is dangerous because it “ionises” atoms – in

other words, it turns them into ions by “knocking off” electrons:

Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.

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Radioactive ContaminationRadioactive Contamination

Timeline of Events

Video of risks from polonium 210

Simply being “irradiated” by a radioactive material doesn’t have to be dangerous – for example, we have background radiation around us all the time. However, being “contaminated” is far more dangerous. Consider the example of Alexander Litvinenko who was poisoned with polonium-210:

19/04/23Other ways of generating Other ways of generating electricityelectricity

Can we drive the turbine directly without burning any fossil fuels?

Here are some examnples...

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Wind PowerWind Power

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Wave PowerWave Power

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Hydroelectric PowerHydroelectric Power

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The National GridThe National GridElectricity reaches our homes from power stations through the National Grid:

If electricity companies transmitted electricity at 230 volts through overhead power lines there would be too much energy loss by the time electricity reaches our homes. To ensure this doesn’t happen, electricity companies transmit electricity at higher voltages instead.

Power stationStep up

transformerStep down

transformerHomes

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Which power station?Which power station?Type of power station

Commiss-ioning costs

Running costs

(p per KWh)

Decommiss-ioning costs

Life span (years)

Coal £650 million 4 £100 million 40-80

Oil £700 million 12 £100 million 40-80

Gas £800 million 6 £100 million 30-40

Nuclear £2 billion 3 £500 million 30-40

1) Which power station is the most expensive to build and why?

2) Give one advantage of coal power stations

3) Why is nuclear fuel cheaper than oil?

4) Overall, which power station is the most expensive?

19/04/23Matching supply and Matching supply and demand…demand…

“Baseline” power stations

Hydroelectric power station might “kick in” here

19/04/23Solar Panels and Thermal Solar Panels and Thermal TowersTowers

What are the advantages and

disadvantages of solar power?

19/04/23Using Solar Energy in remote Using Solar Energy in remote placesplaces

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Geothermal EnergyGeothermal Energy

Geothermal energy can be used in _______ areas such as ______. In a geothermal source cold water is pumped down towards ____ _____. The water turns to steam and the steam can be used to turn ______. In some areas the _____ rising at the surface can be captured and used directly.

Words – steam, Iceland, volcanic, turbines, hot rocks

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Non-renewable energy sourcesNon-renewable energy sources

Coal, oil, gas and nuclear

Advantages Disadvantages

Cheap fuel costs

Short start-up time for gas and oil

Good for “basic demand”

Fuel will run out

Costs a lot of money to

decommission a nuclear plant

Pollution – CO2 leads to global warming and SO2 leads to acid rain

Reliable

Nuclear produces little pollution

19/04/23Renewable energy sources Renewable energy sources summarysummary

Wind, tidal, hydroelectric and solar

Advantages Disadvantages

Zero fuel costs

Hydroelectric is good for a

“sudden” demand

Don’t produce pollution

Tidal barrages destroy the habitats of wading birds and hydroelectric

schemes involve flooding farmland

Unreliable (except for

hydroelectric)

Expensive to build

Solar is good for remote locations (e.g. satellites)

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Electricity Supply in the UKElectricity Supply in the UKNotice that, due to all these advantages and disadvantages, we use a variety of sources of energy in the UK: