Physics Unit 2

Using the Sun's energy
1. The Sun is the ultimate source of loads of our energy
  1. The Sun has been giving out loads of energy-mostly heat and light
  2. Some of that energy is stored here on Earth as fossil fules
  3. We can also use photocells and solar heating
2. You can capture the suns energy using photocells
  1. Photocells generate electricity directly from sunlight
  2. They generate diret current (DC)
    1. Direct current means the current flows the same round the circuit all the time
  3. Photocells are usually made of silicon
    1. The silicon atombs absorb some of the energy, knocking loose some electrons
    2. These electrons then flow round a circuit-which is electricity
  4. The current and power output of a photocell depends on
    1. It's surface area
      1. The bigger the cell the more electricity it produces
    2. The intensity of light
      1. brighter light=more electricity
    3. The distance from the light source
      1. The closer the cell, the more intense the light hitting it will be
  5. Advantages
    1. There are no moving parts
    2. Sturdy, low maintenance and lasts a long time
    3. You don't need power cables or fuel
    4. Solar power won't run out and it does not pollute the enviroment
  6. Disadvantages
    1. No sunlight, no power
3. Curved mirrors can concentrate energy from the sun
Solar and Wind power
1. Passive solar heating
  1. PSH is when energy from the sun is used to heat something directly
  2. Glass lets heat and light in from the sun
2. Wind Farms
  1. Lots of little wind turbines
  2. Uses wind to produce electricity
Producing and Distributing Electricity
1. The national grid connects power stations to consumers
  1. The national grid allows electricity to be supplied anywhere around the country
2. There are different power sources
  1. Fossil Fules
    1. Produces a lot of energy
    2. Releases a lot of carbon-dioxide
  2. Biomass
    1. It is a renewable source
    2. You need a lot of it
  3. Nuclear Power
    1. Does not produce a lot of CO2
    2. Can make a lot of energy without producing a lot of CO2
    3. Risk of leaks and disasters
  4. Photo cells
    1. Advantages and disadvantages in Red
  5. Wind Power
    1. Cheap to run
    2. 1500 turbines=one coal powered stations
The Dynamo Effect
1. Electromagnetic Induction
  1. The creation of a voltage in a wire which is experiencing a change in magnetic field
2. Move the wire or the magnet
  1. Two ways to get EMI
    1. An electrical conductor (a coil of wire is used often) moves through a magnetic field
    2. The magnetic field through an electrical conductor changes (gets bigger, smaller or reverses
  2. To get a bigger voltage
    1. The strength of the magnet
    2. The umber of turns on the coil
    3. The speed of movement
3. Generators move a coil in a magnetic field
  1. Every half turn, the current in the coil swaps direction
    1. This means that generators produces an alternating current (AC)
      1. Turning the coil faster produces
        More pearks
        A higher voltage
        A higher current
        The frequency of AC is measured in Hz
        Electricity in the UK is 50 Hz
        Meaning that the coil is rotating 50 times per second
Supplying electricity efficiently
1. Electricity is transformed to high voltage before distribution
  1. To transmit a lot of power you need
    1. A high voltage
    2. A high current
      1. But a high current means the cables get hot
    3. It is cheaper to increase the voltage
      1. To bring down voltage you need a step-down transformer (AC)
        This is why mains energy is AC so that transformers work
      2. To increase voltage you need a step-up transformer (AC)
2. Power stations aren't very efficient
  1. Power stations make a lot of waste energy
    1. Total Energy=Useful energy output + waste energy output
      1. Efficiency=Useful energy output/total energy input (x 100)
Electrical Power
1. Running costs depend on an appliances power rating
  1. Power (W) = Voltage (V) x Current (A)
2. Kilowatt-hours (kWh) are units of energy
  1. Energy Supplied (kwh) = Power (kW) x Time (H)
    1. Cost = number of units x price per unit
  2. kWh = amount of energy converted by 1 kW appliance left on for 1 hour
3. Off-peak electricity is cheaper
The green house effect
Global warming and climate change
1. Upsetting the greenhouse effect has led to climate change
  1. Evidence shows that the rising of CO2 is causing global warming.
    1. There is a scientific consensus the humans are causing global warming
2. Changes to the weather can have human and natural causes
  1. Changes in temperature can have large effects on weather
    1. Some crops won't be able to grow
Nuclear radiation
1. Nuclear radiation causes ionisation
  1. Ionisation is when alpha, beta or gamma radiation hits atoms causing them to lose (positive) or gain (negative) electrons
    1. Alpha particles are big and heavy
      1. Strongly ionising
      2. Easily stopped
    2. Beta particles are electrons
      1. Moderately ionising
      2. Mediumly stopped
    3. Gamma rays are very high frequency electromagnetic waves
      1. Weakly ionising
      2. Hard to be stopped
    4. When radiation enters human skin it damages cells, can cause mutations
Uses of nuclear radiation
1. Alpha radiation is used in smoke detectors
2. Beta radiation is used in tracers and thickness gauges
3. Gamma radiation has medical and industrial uses
  1. Can treat cancers
  2. Sterilise medical instruments
  3. Non-destructive testing
Nuclear power
1. Nuclear power uses Uranium as fuel
  1. Uranium atoms split in 2
    1. Water used as coolant to produce steam
      1. Steam powers turbine which produces kinetic energy
        This then goes into a generator which creates electrical energy
2. Advantages
  1. Doesn't release alot of CO2
  2. Realises a lot of energy
  3. It is cheap
  4. Plenty of uranium left
3. Disadvantages
  1. Expensive to build and maintain
    1. Expensive to decomision
  2. Longer to start up
  3. Risk of leaks
  4. Uranium non-renewable source
Danger from radioactive matirials
1. You should always protect yourself
  1. Handle with tongs
  2. Store safely
  3. Keep at arms length
  4. Don't look at it
  5. Industrial workers have
    1. Full protective suits
    2. Lead-lined suits
    3. Lead/concrete barriers
    4. Thick lead screens
    5. Remote-control robot arms
2. Radioactive waste is hard to dispose of
  1. High level
    1. Stored underground in glass cases
  2. Low level
    1. Put in land-fill sites
The Solar System
1. Planets reflect sunlight and orbits the sun in ellipses
  1. Our star (the Sun) has lots of stuff orbiting it
    1. Mercury
    2. Venus
    3. Earth
    4. Mars
    5. Asteroids
    6. Jupiter
    7. Saturn
    8. Uranus
    9. Neptune
2. The solar system is held together by gravitational attraction
  1. Gravity pulls everything in the universe towards everything else
    1. Gravity makes things that are already moving change course
Asteroids and Comets
1. There's a belt of asteroids orbiting between Jupiter and Mars
  1. When the solar system was formed the large rocks between Jupiter and Mars didn't form a planet as the large gravitational pull from Jupiter kept interfering
    1. This left millions of asteroids orbiting the sun between Mars and Jupiter
  2. Asteroids usually stay in their orbit but sometimes they are pushed or pulled into others
2. Meteorites are rocks that have crashed down to Earth
  1. As the enter Earth's atmosphere they burn up
    1. These are known as shooting stars
    2. Sometimes, rarely, they don't burn up and they crash into the Earth's surface
      1. They can start fires, throw lots of hot rocks and dust into the air
      2. They make big holes in the ground called craters
      3. The dust and smoke can block out the sun for many months
        This causes climate change and can make animals extinct
3. Comets orbit the sun in very elliptical orbits
  1. Comets are balls of rock, dust and ice which orbit the Sun
    1. They come form objects orbiting around the sun way beyond the planets
      1. As comet approaches Sun, it's ice melts leaving a bright tail of gas and debris which can be millions of KM long
        This is what is seen from Earth
        Comets speed up when the get closer to the Sun as of it's gravitational pull
NEOs and the Moon
1. Near-Earth objects could colloid with Earth
  1. NEOs are meteors or comets that are o course to crash into Earth
    1. Scientist calculate the trajectory of the NEO using powerful telescopes
      1. Small NEO are harmless but the big ones can make an explosion bigger than a nuclear bomb
        We could tr to deflect the NEO using a bomb to nudge it off course
2. The moon may have come from a colliding planet
  1. Scientist think the moon came from another planet colliding with the Earth soon after the planet was formed
    1. In the collision it is believed the Earth core was created when the planets collided
      1. The less dense material was ejected as really hot dust and rocks which orbited the Earth eventually came together to form the Moon
        Evidence to support this
        The Moon has a lower density than the Earth
        It does not have an iron core
        Moon rock contains few substances which evaporate at low temperatures
        Suggesting that the moon was made from hot matirials
Beyond the Solar System
1. We're in the Milky Way Galaxy
  1. Our Sun only one of millions of stars in the Milky Way
  2. Gravity keeps Galaxies together
2. The Universe has more than a billion Galaxies
3. Distances in space are measured in Light Years
  1. Km are hard to measure between Galaxies
    1. Scientists use light years
      1. Light Years=The distance light travels through a vacuum in a year
4. Stars can explode and sometimes leave behind black holes
  1. When a big star runs out of fuel it explodes and what is left it really dense
    1. Sometimes it is so dense nothing can escape it's gravitational pull.
      1. This is called a black hole
    2. Black holes have a
      1. Large mass
      2. Small volume
      3. Very high density
    3. They are not visible not even light can escape it
The origin of the Universe
1. The universe seems to expanding because of redshift
  1. Red shift is when scientists look at what colour galaxies are and this determines how far away it is using the visible light spectrum
    1. The further away the galaxy is the more red it is
    2. There are microwave radiation everywhere-it is known as cosmic background radiation
      1. As the universe and cools, the background cools and drops in frequency
      2. The universe started with the big bang
        This is when all that was in the universe was all gathered in one small space
        It then exploded and started expanding and the expansion continues
        The big bang allows us to see how old the Universe is
        It is about 14 billion years old
        It is hard to estimate as it is hard to tell the change in the speed of expansion since the start
The life cycle of stars
Exploring the solar system
1. We can explore space using manned spacecraft
  1. The solar system is big
    1. Sending a manned spacecraft to Mars would take years
      1. It would have to carry
        A lot of fuel
        This makes it heavy and expensive
        Lots of food, water and oxygen
        To keep the astronauts alive and healty
        A sheild
        To protect the astronauts from radiation
      2. The astronauts will lose bone tissue and muscle wasteage from the low gravity
      3. A tiny area with the same people could become stressful
2. Sending unmanned probes is much easier
  1. Advantages
    1. They don't have to carry food, water and oxygen
    2. Can withstand conditions that humans can't
    3. Without people, more instruments can be fitted
    4. They're cheaper
    5. No one gets hurt if the probe burns up in the atmosphere
  2. Disadvantages
    1. They can't think for themselves
    2. A spacecraft can't do maintenance and repairs-people can
Galileo and Copernicus
1. Ancient Greeks thought the Earth was at the centure of the Universe
  1. Most Ancient Greeks believed the Sun, man and other planets and stars all orbited Earth in perfect circles
    1. The Ptolemaic model was the model of the Universe of the Ancient Greeks until the 1500s
2. Copernican Model
  1. This model states that Earth and the planets orbit around the sun, which is at the centre of our Universe
    1. The idea had been around for 2000 years but it was first published in 1543 in a book by Copernicus
      1. Galileo noticed that Venus has phases-where the amount off the planet that was lit by the Sun seemed to change over time
        Copernicans' ideas weren't very popular as the others had been their for a long time
        The model was also condemned b the church. They claimed that the model went against the bible, and said that Earth was at the centre of the universe
        Evidence for Copernican model increased thanks to more technological advances
        The current model says that the planets still orbit the sun but these orbit are elliptical rather than circular
  2. Galileo fond one of the best pieces of evidence for this theory
    1. Galileo was observing Jupiter using a telescope when he saw some stars in a line near the planet
      1. He looked again and sore that these stars never moved away from Jupiter and seemed to be carried along with the planet
        This suggested they weren't stars but moons orbiting Jupiter
        This showed not everything orbits around the Earth

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Physics Unit 2

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