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Gabbie Jones

on 2 April 2016

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Transcript of P2

When a current ( ) passes through a wire, the wire gets hot... the greater the current, the hotter the wire:
When a transformer increases the voltage, the current is reduced which means there is less heating effect and therefore less energy lost to the environment
The greenhouse effect
Collecting energy from the sun:
ADVANTAGES: robust, low maintenance, renewable
DISADVANTAGES: doesn't produce electricity when too dark or cloudy
2 pieces of silicon- one has an impurity added to produce an
of free electrons
(n type silicon)
, one has and impurity added to produce an
on free electrons
( p type silicon)
This creates a p-n junction
Photons are energy packets from the sun
Photons cause free electrons to move which creates an
electrical current
This could remind you of a photon- a packet of energy from the sun
The output of photocells depend on...
light intensity
surface area exposed
distance from light source (sun)
Passive solar heating
The sun produces very short wavelengths of

however, these short waves can go through glass

the walls and floors of these buildings can absorb and re-radiate the
radiation- keeping it nice and toasty inside

since the walls and floor isn't as hot as the sun, the wavelength re-radiated is longer
p-type silicon
n-type silicon
p-n junction
diagram of passive solar heating
Energy from the wind
ADVANTAGES: a renewable source of energy and doesn't contribute to global warming or pollute the atmosphere

DISADVANTAGES: will not work if it isn't windy or if there is too much wind they will be turned off as it can be damaging to the turbine, can be noisy, some people think it can ruin the view and they can take up a lot of space
Diagram of a photocell
Solar reflectors
Solar reflectors
are big mirrors that reflect the suns energy to a tower that converts it to electricity. The panels get moved by computers to make sure they are always facing the sun
Generating electricity
Bigger currents and voltages
dynamo ^
The current from a
can be increased by:
using a
magnet (NOT
increasing the number of turns on the coil
rotating the magnet faster
The output from a dynamo can be displayed on an
, it shows how the
produced by the dynamo varies with time. The time for one complete cycle is called the period of the
alternating current
magic dynamo ^
oscilloscope ^
Frequency= 1 (divided by) time

Frequency is measured in hertz (Hz)
Energy efficiency
Efficiency is a measure of how well a device transfers energy
Energy in a power station is lost in the boilers, generators and cooling towers
useful energy output
total energy input
practical generators
A simple
consists of a coil of wire rotating between the poles of a magnet. The coil cuts through the
magnetic field
as it spins so a
is produced in the coil. Also a
can be created if the coil remains stationary and the magnets move.
This is the same process

at power stations use.
N magnet
S magnet
Power stations
In normal power stations, fuels are used to heat water
water boils to produce steam
steam at high pressure turns a turbine
the turbine drives a generator
Thus producing electricity
Global warming
Greenhouse gases
Naturally occurring co2
Natural forest fires
volcanic eruptions
decay of dead plants and animal matter
from the oceans
Man-made CO2
burning fossil fuels
cement manufacturing
waste incineration
Water vapor
Half of the
greenhouse effect
is due to water vapor.
Almost all water vapor occurs naturally, only 0.001% is caused by humans.

Methane is produced when organic matter
in an environment lacking oxygen. Natural sources include wetlands, termites and oceans. Man-made sources include mining and burning
fossil fuels,
rice paddies and burying waste in landfills.
Electromagnetic radiation from the sun is has a short wavelength which is absorbed and warms up the Earth, then re-radiates the energy as infrared radiation with a longer wavelength. This longer wavelength radiation is absorbed by the greenhouse gases which warm the atmosphere
Dust warms, Dust cools
Dust in the atmosphere can have opposite effects, it can either:
the smoke from the factories reflects
from the town back to the Earth. The temperature rises as a result
The ash cloud from a volcano reflects
from the sun back into space. The temperature falls as a result
Scientific data about global warming
However, what scientists do not agree on is the extent to which humans are to blame
It is important that decisions about global warming is based on facts, not opinions. Many scientists agree that the evidence supports climate change as the global temperature has steadily risen over the past 200 years
Fuels for power
Measuring power
power=voltage x current
cost of electricity used=energy used x cost per kWh (kilowatt hour)
Cheaper electricity
We pay less for electricity during the night when not as much is needed, but it still has to be produced
Energy sources
Some energy sources are more appropriate than others in particular situations. Some factors include
ease of extraction
effect on the environment
Associated risks
The national grid
The national grid is a series of transformers and power lines that transport electricity from the power station to consumers.
In the , transformers are used to step up the voltage to as high as 400000 v. High voltage leads to... reduced energy loss, reduced distribution costs, cheaper electricity for consumers. Then transformers are used to return the voltage back down to normal for consumers.
Transmission losses
Nuclear radiations
Atoms contain the same amount of
this mean they are neutral
Ionisation involves gaining or losing electrons
When an atom
electrons, it becomes
When an atom
electrons, it becomes
The formation of
can cause chemical reactions... Such reactions may disrupt the normal behavior of molecules inside the body e.g. they may cause strands of
to break or change; protein molecules may change their shape and these effects are potentially harmful
Properties of ionizing radiations
Alpha, beta and gamma radiation come from the nucleus of an atom
Alpha radiation cause most ionization and gamma radiation the least
Alpha radiation is short ranged (a few cm) and easily absorbed by a sheet of card or paper
Beta radiation has a range of about 1m and is absorbed by a few millimeters of aluminium
Gamma radiation is much more penetrating and, although a few centimetres of lead will stop most of the radiation, some can pass through several metres of lead or concrete
Experiments can be done to identify each type of radiation from its penetrating power - when carrying out these experiments background radiation should always be taken into account
Uses of radioactivity
Smoke alarms contain a source of
The radiation ionizes the oxygen and nitrogen atoms in the air which causes a very small electric
that is detected. When smoke fills the detector in the alarm, the air is not so ionized, the current is less, and the alarm sounds
Thickness in a paper rolling mill can be controlled by using a source of
radiation and a detector: The amount of
passing trough the sheet is monitored and the pressure on the rollers adjusted accordingly
Gamma radiation kills
so it can be used for sterilizing medical instruments. It can also be used to check for leaks in pipes and welds
The passage of blood and other substances can be traced around the body using a
nuclear waste
Plutonium is a waste product from nuclear reactors which can be used to make nuclear bombs
Some low level radioactive waste can be buried in landfill sites. High level waste in encased in glass and buried deep underground or reprocessed
Radioactive waste can remain radioactive for thousands of years. It must be stored where it can not leak into natural underground water supplies and hence into lakes and rivers. It is not suitable for making nuclear bombs, but can be used by terrorists to contaminate water supplies or areas of land
Nuclear power
Fossil fuel reserves are not used and greenhouse gasses are not discharged into the atmosphere
Very high maintenance and decommissioning costs, risks of accidents similar to the one at Chernobyl
Exploring our solar system
Our solar system
Comets have very elliptical orbits; They pass inside the orbit of Mercury and go out well beyond the orbit of Pluto
Meteors are made of grains of dust and burn up as they enter the Earths atmosphere. They heat the air around them which makes a glowing streak; these are known as shooting stars
Black Holes
Black holes are formed where large stars used to be. Nothing can escape black holes, not even light, that is why you cant see them. They have a large mass, but are very small
Centripetal force
Moons orbit planets and planets orbit stars because centripetal force acts on them. It acts towards the centre of the circular orbit and gravitational attraction sources it
Exploring the planet
Unmanned spacecraft costs less and do not put astronauts lives at risk
Advantages and disadvantages of an unmanned spacecraft
You have to spend a lot of money in order to make them reliable, because if they break down half way through a mission there is usually no way of fixing them
Spacecrafts carrying humans have to have a lot of food, water and oxygen aboard which increases the mass and the cost
Outside the spacecraft, astronauts have to wear special spacesuits:
A dark visor stop the astronauts being blinded
The suit is pressurized and has an oxygen supply for breathing
The surface of the suit can range from 120 - (-)160 degrees C
Distances in space
Distances in space is very large
x 37400000
The sun is roughly 149,600,000 km away from us, which is roughly this many elephants:
Light travels at 300 000km/s!!
Light takes about 8 minutes to get from the sun to Earth
From our next nearest star, it takes about 4.22 years
Threats to Earth
Asteroids are mini-planets that orbit the sun, most of which are in the asteroid belt in between the orbit of mars and Jupiter
Also you might like to know...
The mass of an object determines its gravitational force. EG.
Jupiter- big mass- big gravitational force...
Asteroids- smaller mass- smaller gravitational force...
Origin of the moon
PS. It isn't made of cheese
Scientists believe our moon was the result of the collision between two planets in the same orbit. The iron core of the other planet melted and joined with the Earths core, less dense rock began to orbit and they joined together to form the moon
Scientific data to support the theory
The average density of Earth is 5500kg/m³ and the moon's average density is only 3300 kg/m³
There is no iron on the moon
The moon has exactly the same oxygen composition as the Earth, but rocks on Mars and meteorites from other parts of the solar system have different oxygen compositions
Evidence for asteroids
2) Many fossils were found under the layer of iridium, but not on top - this could be evidence for dinosaurs becoming extinct because of an asteroid collision
Geologists examine evidence to support the theory that asteroids collided with Earth.
1) Near to a crater, thought to be impacted by an asteroid, quantities of metal iridium was found. This is not normally found on the Earth's crust ,but common in asteroids.
Most comets pass between the orbit of Mercury and well pass the orbit of Pluto. As the comets passes close to the sun, the ice melts and solar winds blow the dust into the comets tail which always points away from the sun
Scientists are constantly monitoring and plotting the paths of comets and other near-Earth-objects (NEOs)
Important information:
Comet- a dirty snowball
Asteroid- a lump of rock
Near-Earth-objects- NEOs
The speed of a comet increases as it approaches the sun and decreases as it gets further away. This is because of the changing gravitational attraction
If a NEO is on a collision course with Earth, it could be the end of life on Earth (NOOOOO!!). To avoid this, one option would be to explode a rocket near to the NEO which could alter its course enough to miss Earth
And Finally...
The Big Bang
The expanding universe
Almost all of the galaxies are moving away from each other with the further galaxies moving fastest
Models of the universe
With the help of the newly invented telescope, Galileo observed four moons orbiting Jupiter. This confirmed that not everything orbited the Earth and supported Copernicus's idea that planets obit the sun.
Roman catholic church didn't support this. After a long time it was finally accepted
17th century: Newton worked on universal gravitation - all bodies are attracted to eachother
Today we believe that gravitational collapse is prevented because the universe is constantly expanding because of the Big bang
Red Shift
When a light source is moving away from the observer, it's wavelength appears to increase which shifts light towards the red end of the spectrum - red shift. When scientists look at light from the sun, there is a pattern of lines across the spectrum. This pattern is observed when they look at light from distant stars but it is closer to the red end of the spectrum. They can use this information from red shift to work out the age of the universe
To summarize - light further away = appears to have longer wavelength (red end of the spectrum), this means universe must be traveling away from us and speeding up - from this, scientists can work out the age of the universe
Star's Life + Death
Swirling cloud of gas and dust = nebula.
Clouds pulled together by gravity. Spinning ball gets hot and starts glowing - protostar (can't be seen because of dust cloud
Gravity causes it to become smaller, hotter and brighter. After millions of years, the core temperature is hot enough for nuclear fission to take place. Hydrogen nuclei join to make helium nuclei - energy is released and star shines bright as long as there is enough hydrogen. Small stars shine for longer because they use the hydrogen up at a slower rate.
What happens at death depends on size of star:
Medium-sized stars e.g the Sun, becomes a red giant:
Core contracts
Outer part cools and goes from yellow to red and expands
Gas shells (planetary nebula) are thrown out
Core becomes a white dwarf - shines very bright - eventually cools and becomes a black dwarf
Large stars become red supergiants:
Core contracts and outer parts expands
Suddenly the core collapses to form a very dense neutron star
There is an explosion called a supernova
Remnants from a supernova can merge to form a new star
The core of the neutron star continues to collapse and becomes even more dense - could form a black hole
Black holes have a very large mass concentrated in a small volume - large density. Large mass means very strong gravitational pull
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