# p1 revision

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• Physics 1
• P1.1
• Transfer of Energy
• Is the emission of Electromagnetic waves
• Occurs when the more energetic particles move from the hotter region to the cooler region and take their   heat energy with them
• Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles
• Condensatio and Evaporation
• Condensatio is where a gas turns into a liquid. As the gas cools   the particles slow down losing kinetic energy.
• Evaporation is when a liquid turns into a gas and the particles escape from the liquid when they are moving in the right direction they can escape
• Types of energy
• -Electrical     -Light            -Sound         -Kinetic         -Nuclear       -Thermal       -Gravitational potential       -Elastic potential       -Chemical
• Specific Heat Capacity
• Energy Transfer (J)= mass (kg) x specific heat capacity (J/kg degrees c) x temperature change (degrees c)
• Untitled
• Rate of heat transfer
• The rate depends on many things such as:         -the bigger the surface area              -different volumes         -type of material
• Vacuum Flasks:        Double walled with a vacuum in-between to prevent all conduction and convection. The walls either side of the vacuum and silver and shiny to reduce radiation. The bottle is also insulated with insulating foam to reduce conduction
• P1.2/3
• Energy and Efficiency
• Efficiency of machines
• Most energy transfers involve some losses, often as heat.
• Useful devices are only useful because they can transform energy from on form to another
• The less energy that is 'wasted' the more efficient the device is deemed to be.
• Calculating efficiency
• Efficiency = Useful Energy out divided by total energy in (x 100 for percent)
• Cost Effectiveness
• Example: Light bulbs. A low energy light bulb i 4 times more effective than an ordinary light bulb. Energy Efficient light bulbs are more expensive to by but last longer.
• LED light bulbs are the most efficient but don't give of the same amount of light as the other types.
• Replacing appliances  is  good because new efficient devices are cheaper to run than older less efficient devices. However they are expensive to buy
• Waste energy's uses
• Heat exchangers reduce the amount of heat energy which is lost.
• This is done by pumping cool fluid through the escaping heat. The temperature of the fluid rises and the energy is collected and converted into a form of energy that is useful again
• Waste energy's uses
• Heat exchangers reduce the amount of heat energy which is lost.
• This is done by pumping cool fluid through the escaping heat. The temperature of the fluid rises and the energy is collected and converted into a form of energy that is useful again
• Energy Transformatio diagrams
• Example Sankey diagrams
• It shows how much of the total energy in is being usefully employed compared with how much is being wasted. The thickness of the arrow represents the total amount of energy in. The downwards arrows are wasted and ones going along represents the useful energy
• You don't always know the exact amounts however from the size of the arrows you will be able to have an ideas about proportions of wasted and useful energy
• Energy (kWh) = power (kW) x time (h)
• Cost = No. of Units (kWh) x Price per Unit  (p)
• P1.4
• Generation of electricity
• Renewable and non renewable
• Non-renewable sources will run out one day.               -Coal, oil, natural gases and nuclear fuels (uranium and plutonium)
• Renewable energy sources will never run out.               -Wind, Waves, Solar, Tides, HydroelectricGeothermal, Food , Bio fuels
• Energy sources (renewable)
• Wind Power. This involves wind turbines which are exposed in places such as moors. Each wind turbine has a generator where electricity is generated directly from the wind.
• -spoils the view                 -you need about 1500 to replace 1 coal power station          -very noisy         -no power when the wind stops so you can't increase supply with demand          -initial costs are high
• +minimal running costs    +no pollution +there is no permanent damage to the landscape so when they are removed the view returns to normal
• Solar Cells.    They generate electricity directly from sun light. Solar power is often used in remote places.
• + no pollution +very reliable source of energy   +energy created is free              + no damage to the envirment
• -Initial costs are high        - only generate electricity on a very small scale             -not practical for the national grid
• Hydroelectric Power. This requires flooding and building a big dam. Rainwater is caught and allowed through turbines.
• - can flood the valley      -very unsightly       -initial costs are high
• +little pollution        +can provide an immediate response to increase in demand
• Pumped storage. Water is released through a turbine to a lower reservoir which is then pumped back up to the main reservoir
• -isn't generating just storing
• + can be released during peak times             +Supply a steady demand
• Wave Power. The waves movement displaces the air in a container and this makes a turbine move because the air is displaced by water
• -spoiling the view              -hazard for boats             -unreliable     -initial costs are high
• +no pollution +provide energy on a large scale       +minimal running costs
• Tidal Barrages. They are big dams built across river estuaries. As the water is allowed through the turbines at a controlled speed.
• + minimal running costs    +reliable   +no pollution
• -height of the tide can vary -some tides can provide significantly less energy
• Geothermal energy. This is only possible over volcanic rocks. The hot water and steam rises and goes through turbines which collect the energy
• -aren't a lot of suitable locations for the power plants             -cost of building it is high compared to the energy you get out of it
• +free energy +no real environmentaproblems +heat things directly
• Biofuels. Used to generate electricity by burning them to heat up water. They can also be used  in some cars.
• + they are better from the environment than fossil fuels.
• - initial costs can be high  -not widely accepted      -large areas of forest have been cleared to grow them
• Carbon capture can reduce the impact of carbon dioxide. This involves collecting the CO2 before it is released into the atmosphere
• The National Grid
• It takes power form power stations to where it is needed in homes or industry.
• The transformers have to step up the voltage at one end for efficient transmission.At the other end the step the voltage down to safe useable levels.
• It needs to be able to generate electricity to the demand of the consumer
• P1.5
• Waves
• Wave basics
• The amplitude is the displacement from the rest position from the crest
• Wave length is the length from crest to crest.
• Frequency is the number of ways passing through a certain point per second
• In transverse waves the vibration are perpendicular to the direction of energy transfer of the wave. (hippy)
• In longitudinal waves the vibrations are parallel to the direction of energy transfer of the wave. They have compressions which make the waves move.(Long-i-tud-inal)
• Wave Speed (m/s)= Frequency (Hz) x Wavelength (m)
• Wave properties
• All waves can be reflected, refracted and diffracted. When waves arrive at an obstacle their direction of travel can be changed.
• Reflection of light is what allows us to see objects:light bounces off them and into our eyes. When light travels in the same direction reflects on an uneven surface the light reflects of at different angles. When the surface is smooth you get a clear rejection.
• Angle of incidence = angle of reflection
• Diffraction: all waves spread out at the edges when they pass through a gap. The amount of diffraction depends on the size of the gap.
• Refraction means changing the speed of a wave can change the waves direction. When a wave crosses a boundary between two substances it changes direction.
• Electro magnetic
• Spectrum: Radio waves, micro waves, infrared, visible light, ultra violet, x-rays, gamma rays
• Radio waves are mainly used for communication. Long-wave radio wavelengths can diffract around hills, into tunnels and can also travel long distances.
• Micro waves are used for satellite communication and mobile phones. Micro waves are good because they can pass through the earths watery atmosphere.
• Infrared waves are used for remote controls and optical fibres. Remote controls work by emitting different patterns of infrared waves to send different commands
• Visible light is useful for photography.The camera lens focus' on the visible light.
• Sound waves
• Sound travels as a wave. They are caused by vibrating objects and are a type of longitudinal wave
• Sound waves can reflect and refract. Sound waves will be reflected by hard flat surfaces which is most noticeable in a empty room.
• The higher the frequency the higher the pitch.
• The Origin of the Universe
• The universe seems to be expanding and there are many evidences for this
• Light from other galaxies is red shifted. This is where as stars get further and closer which means the frequency of the waves change and we can tell how they move
• One theory for the origin of the universe is the big bang.  A big explosion happened which then started expanding. Evidence for this is the cosmic microwave background radiation.
• By Charlotte Evans 10T