Download Unit P1 - Universal Physics 2

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Reflection nebula
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Planetary nebula
(This nebula is smaller and will only form a planet)
Stage 2: Protostar
Gravity will slowly pull these
particles together…
As they move inwards
their gravitational
potential energy is
converted into heat and
a PROTOSTAR is formed
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Stage 3: Main Sequence
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In a main sequence star the
forces of attraction pulling
the particles inwards are
_________ by radiation
pressure acting outwards due
to the huge __________
inside the star.
Stars are basically ________ reactors that use _______
as a fuel. During its main sequence a star will release
energy by converting hydrogen and helium (light elements)
into _________ elements.
Our sun is an example of a main sequence star –
it’s in the middle of a 10 billion year life span
Words – heavier, balanced, hydrogen, nuclear, temperatures
Stage 4: Red Giant
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Eventually the hydrogen and helium will run out. When
this happens the star will become colder and redder and
start to swell…
If the star is relatively small
(like our sun) the star will
become a RED GIANT
If the star is big (at
least 4 times the size of
our sun) it will become a
RED SUPERGIANT
Stage 5: The Death
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What happens at this point depends on the size of the
star…
1) For SMALL stars the red giant will collapse under its
own gravity and form a very dense white dwarf:
Red giant
White dwarf
Black dwarf
2) If the star was a RED
SUPERGIANT it will shrink and
then EXPLODE, releasing massive
amounts of energy, dust and gas.
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This explosion is
called a
SUPERNOVA
Before
After
The dust and gas on the outside
of the supernova are thrown
away by the explosion and the
remaining core turns into a
NEUTRON STAR.
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If the star is big
enough it could
become a BLACK
HOLE.
Stage 6: Second generation stars
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The dust and gas thrown out by a supernova can be used to
form a new star…
Our sun is believed to be a “______ ______ star” – this is
because it contains some __________ elements along with
hydrogen and ________. These heavier elements would have
been the products of a previous star that have been thrown
out by a ________. These heavier elements are also found on
planets, indicating that they might have been made from
remains of previous _______ as well.
Words – helium, heavier, second generation, stars, supernova
The formation of the universe
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There are two main theories about how the
universe started:
The “Steady State” theory
This theory states that the universe has always existed as it
does now and hasn’t changed. The trouble is that the night
sky would be completely lit up because of the billions of stars,
but it’s not, so…
The “Big Bang” theory
This theory states that the universe started off with an
explosion and everything has been moving away ever since.
There are two main pieces of evidence for this: background
microwave radiation and red shift.
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Evidence about the origins of
the universe…
Microwaves
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When the “Big Bang” happened microwaves were produced and
these are still reaching us now. They can sometimes be seen
as TV interference.
Red Shift explained
Source of
light
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“Spectra”
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If you pass the light through a gas something
different is seen…
helium
Some wavelengths of light
are absorbed by the gas –
an “absorption spectrum”.
If the light source is moving away the absorption
spectra look a little different…
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Before
helium
helium
After
The absorption lines have all been “shifted”
towards the longer wavelength end (red end)…
This is called red
shift. The faster
the light source
moves the further
its light will be
“shifted”
Before
After
A similar effect happens with sound –
this is called “The Doppler Effect”
Hear Doppler Effect
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Red Shift simplified
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Basically, if I walk towards you I’ll look
slightly more blue. Then, if I walk away
from you, I’ll look slightly more red!!
Let’s try it…
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Light from different stars and from the edge
of the universe also shows this “red-shift”.
This suggests that everything in the universe
is moving away from a single point.
This is the BIG
BANG theory
Red shift summary
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Light from other galaxies has a longer _________ than expected. This
shows that these galaxies are moving ____ from us very quickly. This
effect is seen to a greater extent in galaxies that are _______ away from
us. This indicates that the further away the galaxy is, the ______ it is
moving.
This evidence seems to suggest that
everything in the universe is moving
away from a single point, and that this
process started around 14 _____ years
ago. This is the ____ ________
Theory. Further evidence of this
theory is Cosmic Microwave Background
Radiation (CMBR) – this radiation comes
from the Big Bang and fills the
_________.
Words to use – faster, away, universe, big
bang, billion, wavelength, further
Big Bang Theory vs Steady State
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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.
However, the discovery of
CMBR was the final nail in
the coffin for the Steady
State theory. So, Mr
President, the Big Bang
theory is now the widely
accepted theory of how
the universe began.
Stephen Hawking, 1942 -
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Topic 4 – Waves and the Earth
Ultrasound
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Ultrasound is the region of sound above 20,000Hz – it can’t
be heard by humans. There are a number of uses for
ultrasound:
1) Pre-natal scanning
1) Sonar
2) Communication between animals
Pulse-Echo techniques
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In pulse-echo techniques sound is reflected from an object to
measure the distance to that object:
Pulse-Echo techniques - Ultrasound
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Ultrasound is the region of sound above 20,000Hz – it can’t
be heard by humans. It can be used in pre-natal scanning,
sonar techniques and as communication between _______:
How does it work?
Ultrasonic waves are partly _________ at the boundary as they pass from
one _______ to another. The time taken for these reflections can be
used to measure the _______ of the reflecting surface and this
information is used to build up a __________ of the object.
Words – depth, reflected, picture, medium, animals
The Maths of Pulse-Echo
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Consider shouting at a wall:
x
The speed of sound is given by:
Therefore
v = 2x/t
x = vt/2
The Maths of Pulse-Echo
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The echo takes 0.8 seconds to return
and the speed of sound in water is
1500ms-1. How deep is the water?
25 50 75 100 125 150 175 200
t/μs
Use the ultrasound scan to determine the width of the amniotic sac and
the width of the baby’s body. The speed of sound in the fluid is 1500ms-1
and in soft tissue the speed is 1560ms-1.
Using an oscilloscope with ultrasound
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Consider a block of
metal with a flaw:
20ms/div
Q. If the speed of the ultrasonic wave is 3,000m/s how
far away is the flaw from the detector?
Infrasound
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Infrasound is the region of sound BELOW 20Hz (as opposed to
ULTRASOUND which is above 20KHz) – it can’t be heard by
humans. Some uses:
1) Communication between animals
African elephants use infrasound to
communicate with other elephants many
kilometres away.
2) Detecting movement in remote areas
3) Detecting volcanic eruptions and
meteors
The Structure of the Earth
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A thin crust 10-100km thick
A mantle – has the
properties of a solid
but it can also flow
A core – made of
molten nickel and iron.
Outer part is liquid
and inner part is solid
How do we know this? These facts have all been
discovered by examining seismic waves (earthquakes)
Seismic waves
Earthquakes 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
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Seismic waves
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These P waves are
being reflected at the
crust
These P waves travel
through the Earth and
are refracted when
they pass through a
medium
The paths of these waves are all
curved because density is
gradually changing
These S waves cannot
travel through the
outer core as they only
go through solids
Locating Earthquakes
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By measuring the time
it takes the wave to
travel to these
locations the location
of the earthquake can
be found.
Movement of the Crust
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The Earth’s _______ is split up into different sections
called ________ plates:
These plates are moving apart from each other a
few centimetres every _______ due to the
________ currents in the mantle caused by the
________ decay of rocks inside the core.
Words – radioactive, crust, convection, tectonic, year
Plate Movements
Earthquakes and
volcanic eruptions can
be common here
Igneous Rock
Oceanic Crust
Mantle
Convection
Currents
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Magma
Topic 5 – Generation and
Transmission of Electricity
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Electric Current
Electric current is a flow
of charge around a circuit
+
-
e-
Note that
electrons go
from negative
to positive
and are
“pushed” by
the voltage
By definition, current is “the
rate of flow of charge”
e-
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Basic ideas…
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Electric current is when electrons start to flow around a
circuit. We use an _________ to measure it and it is
measured in ____.
Potential difference (also called _______) is
how big the push on the electrons is. We use a
________ to measure it and it is measured in
______, a unit named after Volta.
Resistance is anything that resists an electric current. It is
measured in _____.
Words: volts, amps, ohms, voltage, ammeter, voltmeter
More basic ideas…
If a battery is
added the current
will ________
because there is a
greater _____ on
the electrons
If a bulb is added
the current will
_______ because
there is greater
________ in the
circuit
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Electrical Power
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Power is defined as “the rate of transferring energy” and is
measured in units called “Watts” (W).
The amount of power being transferred in
an electrical device is given by:
Power = voltage x current
in W
in V
in A
P
V
I
1) How much power is transferred by a 230V fire that runs
on a current of 10A?
2) An electric motor has a power rating of 24W. If it runs
on a 12V battery what current does it draw?
3) An average light bulb in a home has a power rating of
60W and works on 230V. What current does it draw?
Fuels
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A “fuel” is something that can be burned to release heat and
light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In
other words, they were made from fossils.
Some definitions…
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A renewable energy source is clearly one that can be
_______ (“renew = make again”), e.g. _____, solar power
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 nonrenewable but NOT a fossil fuel.
Words – non-renewable, coal, fossil
fuels, wood, renewed
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Using non-renewable fuels in power stations
1) A fossil fuel is burned in the boiler
2) Water turns to steam and the steam drives a
turbine
3) The turbine turns a generator
4) The output of the generator is connected to a
transformer
5) The steam is cooled down in a cooling tower and
reused
Efficiency of Power Stations
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Heat
100J
Boiler
85J
Heat
Heat
Turbine
35J
Kinetic
Heat
Generator
30J
Electrical
Pollution
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When 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
Nuclear power stations
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These work in a similar way to normal power stations:
The main difference is that the nuclear fuel is NOT
burnt – it is used to boil water in a “heat exchanger”
Start up times
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Different power stations have different start up times:
Gas
Quick
Oil
Coal
Nuclear
Slow
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Non-renewable energy sources
Advantages
Disadvantages
Pollution – CO2 leads
to global warming and
SO2 leads to acid rain
Cheap fuel costs
Generate a lot of
energy
Easy to use
Coal, oil, gas and
nuclear
Fuel will run
out