Physics 1.2

Energy Sources
1. Non Renewable Energy Sources: 1) Coal 2) Oil 3) Natural gas 4) Nuclear fuels (uranium/plutonium) ...a) They will all run out b) They all damage the environment c) They provide most of our energy
  1. Fossil Fuels: In a fossil fuel power station the fuel is burnt and the heat produced turns water into steam. The pressured steam turns a turbine. +It is a quick process. +It is cheap. +It is easy to get. -It is non-renewable. -It gives off carbon dioxide.
  2. Nuclear Fission: In a nuclear reactor atoms of uranium or plutonium undergo nuclear fission. This creates a huge amount of energy as heat, heat turns into steam.+Huge amounts of energy. +No carbon dioxide. +The fuel wont run out for hundreds of years. -Creates lots of waste. -Can cost a lot. -Takes a long time to generate the energy. -Risk-could release radio-active waste.
2. Renewable Energy Sources: 1) Wind 2) Waves 3) Tides 4) Hydroelectric 5) Solar 6) Geothermal 7) Food 8) Biofuels...a) These will never run out. b) they damage the environment in a less nasty way than non-renewable. c) They don't provide much energy and some are unreliable.
  1. Geothermal Power: In some parts of the World (Iceland) that are close to Volcanic areas, steam rises to the Earths surface and can be piped directly to a power station. +Does not have any fuel costs. +Releases no Carbon Dioxide. -Can only have them in a few areas.
  2. Biomass/Biofuels: All forms of biomass involve material produced by living organisms. This is then burnt and steam is created. +Costs very low. +Can also supply hot water. +Carbon neutral. +Renewable. -Release atmospheric pollutants. -Could contribute a great deal to global warming. -Quite expensive-producing biomass and converting to alcohols.
  3. Solar: Solar cells generate a direct current when light energy is absorbed by them. They transfer light energy into electrical energy and produce a direct current. +Inexhaustable fuel source. +No pollution. +Often an excellent supplement to other renewable sources. +Can be used for powering other items: solar cars/satellites. -Low energy production-would have to have lots of them to produce a decent amount (more money). -Only areas with lots of sunlight would be suitable.
  4. Wind: Winds are convection currents set up in the Earths atmosphere by energy from the sun. The kinetic energy of wind drives wind turbines directly. +Inexhaustable fuel source. +No pollution. +Often excellent supplement to other renewable sources. -Low energy production (would have to have lots-more money). -Noisy -Only suitable for windy areas. -Can be expensive to maintain.
  5. Tidal/Wave: As the waves move up and down, water is allowed to flow through turbines in the barrage to generate electricity. +Can reduce carbon emission. +It is renewable. +As waves are so powerful, tidal turbines can be small but still produce a lot of energy. +Not too expensive. -The tides in an area have to meet the required size to make enough energy. -Destruction of sea life. -Can be unreliable as waves aren't always big.
  6. Hydroelectric: A hydroelectric power station turns kinetic energy from water into electrical energy. A dam is built in a hilly area and the water is collected into pipes down hill. +Inexhaustable fuel source. +Minimal environmental impact. +Useful levels of energy production. +Can be used throughout the World. -Smaller models depend on availability of fast flooding streams. -Can have an impact on river life.
3. Carbon neutral: When a plant is burnt and another one is planted it causes a balance in the Carbon dioxide levels. Carbon capture: Where the carbon is captured and put underground (where it came from) so it doesn't get into the atmosphere.
Powerstations
1. The National Grid: Step up transformer- increase voltage, decrease current. Step down transformer- decrease voltage to make it safe.
  1. The national grid is anything that involves transporting power/electricity from power stations to homes.
2. Advantages of putting electric cables underground: +It is out of the way. +Not open to storms. +Can't see it (not an eye-sore). +Not dangerous for firemen/people.
3. Advantages of pilons: +Not open to flooding/water damage. +Easier to maintain. +Don't have to dig up areas around it. +Cheaper.
Disadvantages of Energy Sources
1. Non renewable disadvantages: 1) fossil fuels-green house gasses-global warming. 2) Burning coal/oil-sulfur dioxide-acidic rain. 3) Coal mining-mess of the landscape. 4) Oil spillages- serious environmental problems (effecting mammals/birds). 5) Nuclear power-waste can be dangerous. 6) Nuclear fuel- cheap but overall cost is high because of power plant and final decommissioning. 7) Nuclear power always carries the risk of major catastrophe.
2. Renewable disadvantages: Biofuels-lots of forest areas have to be cleared so lots of species lose their habitat. The decay and burning of this also increases carbon dioxide and methane emissions.
Wave Basics
1. Frequency is the number of complete waves passing a certain point per second. Frequency is measured in hertz (Hz). 1 Hz is 1 wave per second.
  1. Wave speed = frequency x wavelength... (m/s) = (Hz) x (m)...v = f x λ
2. Transverse waves: 1) Light and all other EM waves. 2) Ripples on water. 3) Waves on strings. 4) A slinky spring wiggled up and down. IN TRANSVERSE WAVES THE VIBRATIONS ARE PERPENDICULAR (AT 90o) TO THE DIRECTION OF ENERGY TRANSFER OF THE WAVE.
3. Longitudinal waves: 1) Sound waves and ultrasounds. 2) Shock waves e.g. seismic waves. 3) A slinky spring when you push the end. IN LONGITUDINAL WAVES THE VIBRATIONS ARE PARALLEL TO THE DIRECTION OF ENERGY TRANSFER OF THE WAVE.
  1. Sound waves
    1. Sound waves are caused by vibrating objects. These vibrations are passed through the surrounding medium as a series of compressions. These will eventually travels through someones inner ear and reach their eardrum where they will hear the sound. The denser the medium the faster the sound travels, sound generally travels quicker in solids then liquids and quicker in liquids then gases. Sound can't travel in space because its mostly vacuum (no particles).
      1. Sound waves will be reflected by hard flat surfaces, this is why a large empty room sounds different to one with things in. That's because these things absorb the sound and stop it echoing. Echos are just reflected sound waves. You hear a delay between the original sound and the echo because the echoed sound waves have to travel further so take longer to reach your ears. Sound waves will also refract as they enter different mediums-in denser materials they speed up.
        High frequency sound waves sound high pitched. Low frequency sound waves sound low pitched. Frequency is the number of complete vibrations each second and is measured in Hz. High frequency means shorter wavelength. The loudness of a sound depends on the amplitude therefore the bigger the amplitude the louder the sound.
Wave Properties
1. All waves can be reflected, refracted and diffracted, this happens when waves arrive at an obstacle (or meet a new material) and their direction of travel can be changed.
  1. Refraction
    1. Refraction is when waves go through a new material and change direction. Waves will only be refracted if they meet a new medium at an angle. If they're travelling along the normal they will change speed but not direction.
      1. If light travels through a medium and goes from fast to slow the angle of refraction gets smaller. But if the light goes from slow to fast the angle of refraction gets bigger.
  2. Diffraction
    1. When a wave spreads out after passing through a gap or past an object. The amount of diffraction depends on the size of the gap relative to the wavelength of the wave. The narrower the gap, or the longer the wavelength. the more the wave spreads out. A narrow gap is one that is the same order of magnitude as the wavelength of the wave (about the same size). So whether a gap counts as narrow or not it depends on the wave in question. Light has a very small wavelength (about 0.0005mm) so it can be diffracted but needs a really small gap.
  3. Reflection
    1. Reflection of light is what allows us to see objects, light bounces off them into our eyes. When light travelling in the same direction reflects from an uneven surface such as a piece of paper, the light reflects off at different angles. When light travelling in the same direction reflects from an even surface (smooth and shiny like a mirror) then its all reflected at the same angle and you get a clear reflection. ANGLE OF INCIDENCE = ANGLE OF REFLECTION.
      1. 1) The image is the same size as the object. 2) It is as far behind the mirror as the object is in front. 3) The image is virtual and upright-it is virtual because the object appears to be behind the mirror. 4) The image is laterally inverted-the left and right sides are swapped.
Electromagnetic Waves
1. EM waves with different wavelengths have different properties. We group them into seven basic types but the regions merge together to form a continuous spectrum. EM waves vary in wavelength however they all travel at the same speed (3 x 10(8)m/s) in a vacuum. EM waves with higher frequencies have shorter wavelengths. Because they have different different properties they are used for different purposes.
  1. EM SPECTRUM
  2. Radio waves are EM radiation with wavelengths longer than about 10cm. Long-wave radio (1-10Km) can be transmitted and received from half way around the World, that's because long wavelengths diffract around the curved surface of the Earth. They can also diffract around hills and into tunnels. This diffraction effect makes it possible for radio signals to be received even if the receiver isn't in line of the sight of th transmitter. The radio waves used for TV and FM radio transmissions have very short wavelengths (10cm-10m). To get reception you must be in direct sight of the transmitter (doesn't bend round hills etc.). Short-wave radio (10m-100m) can be received long distance because they are reflected from the ionosphere (electrically charged layer in the Earth's upper atmosphere). Medium wave signals can also reflect from the ionosphere (depending on atmospheric conditions and time of day.
  3. Microwaves are used for satellite communication and mobile phones. The microwaves used for this need to be able to pass through the Earth's watery atmosphere (radio waves can't). For satellite TV, the signal from a transmitter is transmitted into space where it is picked up by the satellites receiver dish orbiting the Earth. The satellite transmits the signal back to Earth in a different direction where it is received by a satellite dish on the ground. Mobile phone calls also travel as microwaves between your phone and the nearest transmitter. Also microwaves are used by remote-sensing satellites-to 'see' through the clouds and monitor oil spills, track the movement of icebergs and see how much rain forest has been chopped down.
  4. Infrared Waves are used for remote controls and optical fibres. Infrared waves are used in lots of wireless remote controls, remote controls work by emitting different patterns of infrared waves to send different commands. Optical fibres can carry data over long distances very quickly. They use infrared waves and visible light. The signal is carried as pulses of light or infrared radiation and is reflected off the sides of a very narrow core from one end of the fire to another.
  5. Visible lens is useful for photography. Cameras use a lens to focus visible light onto a light sensitive film or electronic structure. The lens aperture controls how much light enters the camera, the shutter speed determines how long the film or sensor is exposed to the light. These make it possible to capture as much light as you want in a photograph.
Origin of the Universe
1. Light from other galaxies is red sifted. Different chemical elements absorb different frequencies of light. Each element produces a specific pattern of dark lines at the frequencies that it absorbs in the visible spectrum. When we look at light from distant galaxies we can see the same patterns but at slightly lower frequencies than they should be-they're shifted towards the red end of the spectrum-red shift. Measurements of the red-shift suggest that all the galaxies are moving away from us very quickly. More distant galaxies have greater red-shifts than nearer ones. This means more distant galaxies are moving away quicker than nearer ones. This provides evidence the whole universe is expanding.
  1. The Doppler Effect: When something emits waves moving towards you or away from you the wavelengths and frequencies of the waves seem different-compared to when its stationery. Moving towards you: Higher frequency, Shorter wavelength. Moving away from you: Lower frequency, Longer wavelength.
    1. The BIG BANG: According to this theory, all matter and energy n the universe must have been compressed into a very small space. Then it exploded from that single 'point' and started expanding. The expansion is still going on and we can use this expansion to estimate its age (14 Billion years old). The STEADY STATE theory says that the universe has always been existed as it is now and always will do. Its based on the fact that the universe seems the same pretty much everywhere. The theory explains the apparent expansion by suggesting that matter is being created in the spaces as the universe expands. the discovery of CMBR was strong evidence that the Big Bang theory was the more likely explanation of the 2.
      1. The big bang theory also has its limitations. for example for complicated reasons the Big Bang theory predicts the universe's expansion should be slowing down however its actually speeding up. It also doesn't explain what actually caused the explosion or what conditions were like before the explosion (if there was one). It seems that the Big Bang theory will be adapted to alter its weaknesses rather than completely forgot about as it explains so much.
        CMBR is cosmic microwave background radiation. Scientists detected low frequency electromagnetic radiation coming from all parts of the universe (CMBR). Just after the Big Bang while the universe was still extremely hot, everything in the universe emitted high frequency radiation. As the universe expanded it has cooled, and this radiation has dropped in frequency and is now seen as microwave radiation.

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Physics 1.2

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	Criado por ellielouise7 aproximadamente 11 anos atrás