Izzy Gray PHYSICS P1

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  • Created by: izzygrayx
  • Created on: 16-01-17 16:13
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  • Physics P1
    • Energy
      • Energy is measured in Joules (J). Energy cannot appear or disappear but sent into the surroundings.
      • It isn't a physical substance.  The mass of chemicals is the same but the amount stored is different. Energy cannot exist in different forms.
      • Infrared Radiation: All objects emit and absorb I.R. Shiny light colored surfaces absorb I.R. slower than black matt surfaces. They reflect it well. Hotter surfaces emit radiation faster.
      • Infrared Radiation and Global Warming: One theory is that sea water is dark colored and will absorb I.R from the sun faster than ice does.
    • Kinetic Theory
      • Bonds between particles are strongest in solids and weakest in gases.
      • Melting- Solids to Liquid. The solid heats up, particles vibrate, bonds break and reform to change places.
      • Freezing- Liquid cools to solid.
      • Boiling- Liquid to a gas when heated. The particles break bonds and move around.
      • Condensing- Gas cools and changes to liquid.
      • Solids- Particles vibrate & have strong bonds. In Liquid- particles move around but have weak bonds. In Gases- Particles move randomly & have weak bonds.
      • Conduction and Convection: Conduction: Transfers energy from one particle to another through solid. Convection: When a part of a liquid or gases is warmed and particles vibrate more, the warm region expands and it becomes less dense and begins to rise.
      • Metals are good conductors as they have electrons that are free to move rapidly from hot to cold regions which transfer energy.
    • Evaporation and Condensation
      • Evaporation- Liquid changes to gas at a lower boiling point.
        • It's quickest if its warm, If the liquid has a large S.A, or its windy.
        • At high altitudes, wind speeds are high and air pressure is low. Easier for particles to evaporate.
      • Water evaporates from earths surface-cools-clouds formed-water vapour condenses into liquid rain- WATER CYCLE.
      • Hot objects cool- energy is transferred TO surface by conduction and FROM the surface by convection.
        • The ratio of surface area to volume affects the rate of heat loss. Larger the surface area>>the quicker energy is transferred.
    • Insulating Buildings
      • Payback Time- Time taken to save as much money as it costs to install an energy saving measure.
      • PAYBACK TIME>> Installation cost/ annual saving.
      • Energy is Transferred TO or FROM a material (J)= Mass(Kg) x Specific Heat Capacity (J/Kg) x Temperature change (Degrees C)
      • Oil filled radiators use specific heat capacity- 2000 J/Kg.
    • Energy Transfer and Waste
      • The Law of Conversation of Energy says energy cannot be created or destroyed. USE SANKEY DIAGRAM.
      • Efficiency= Useful Energy Out/ Total Energy In.
        • CONVERT DECIMAL TO %= x100
    • Electrical Appliances
      • Mains electricity is convenient, safe and pollution free at point of use. But generating electricity in power stations causes POLLUTION.
      • Alternatives to electricity: gas or biomass for cooking, lighting and transport.
      • LEDs produce LIGHT. Electrons in materials used to make LEDs ABSORB energy from voltage. Then released as light.
        • The COLOUR of light from LEDs depends on the ENERGY RELEASED by the ELECTRONS inside it.
      • Energy used in an appliance: Power (W) x Time (s)
      • Connecting cables-Designed to heat up as little as possible when carrying current- so little energy is put into surroundings.
    • Cost of Electricity
      • Kilowatt-hour= Power (kW) x Time (hrs)
      • Cost of using Electricity= Number of kilowatt-hours used x Cost per Kilowatt-hour.
      • Power Station: Fossil fuels are burned or(nuclear fuels undergo fission), water heats, turns to steam, steam drives turbines, spin generators, generates electricity.
        • Using more efficient power stations reduces environmental damage as they use LESS fuel and produce LESS emissions of electricity generated.
    • Renewable Energy
      • Will NOT run out. These resources spin turbines directly: When the wind blows, it spins blades on wind turbine.
      • Steam drives turbines in biomass & geothermal power stations: Biomass is organic waste that's burned.
      • Hydroelectricity can cause more GLOBAL WARMING than fossil fuel power stations as vegetation rots at the bottom of the reservoir and its edges.
    • Making Comparisons
      • The National Grid uses aluminium cables reinforced with steel- conduct electricity well.
      • Fossil fuel stations are cheaper to build but operating costs will increase as supplies of fossil fuels fall.
      • Fossil fuel and nuclear fuels can be stored-increasing reliability.
      • Solar cells, wave and wind turbines are WEATHER DEPENDENT so less reliable.
      • Nuclear power stations have the longest start up and shut down times, followed by coal then gas power stations.
    • Waves
      • Waves transfer energy from a source without transferring MATTER.
      • Longitudinal waves oscillate in the SAME direction that the energy travels & include sound waves.
      • Transverse waves oscillate at right angles to the direction the energy travels & include electromagnetic waves, water waves
      • SEISMIC waves are mechanical waves- transfers energy from earthquakes.
      • Primary- Longitudinal. Secondary- Transverse.
      • Waves can be REFRACTED (Change direction at boundary)- waves refract because they change SPEED in different materials.
      • If a wave moves into a material where it travels slower, the wave refracts TOWARDS the normal.
        • The NORMAL-A line drawn at right angles to a surface.
      • Raindrops refract sunlight. Blue refracts more than red.
    • Waves and Movement
      • When light, sound or microwaves move away from an observer, the wavelength INCREASE and frequency DECREASES
      • If it moves towards an observer, the wavelength DECREASES and frequency INCREASES.
        • DOPPLER EFFECT
          • When light, sound or microwaves move away from an observer, the wavelength INCREASE and frequency DECREASES
      • IF THE WAVELENGTH OF LIGHT OR SOUND INCREASES, ITS FREQUENCY DECREASES.
      • RED SHIFT: Light from many galaxies is SHIFTED TOWARDS the red end of the spectrum it appears to have a LONGER wavelength than light from own
      • The Big Bang theory suggests that the universe began from a very small initial point where all energy and matter were concentrated. It then expanded violently.
      • The RED SHIFT is evidence that the universe is still expanding- also Big bang theory.
      • CMBR is electromagnetic radiation filling universe. Big Bng is the only theory to explain this existence.
    • Cable and Digital
      • Analogue signals- any value. Digital signals- pulses only have 2 values, on of off.
      • Digital signals are higher quality as: less interference between different D.S., D.S quality isn't affected by distance, be made stronger.
      • Fibre optic cables transmit information fast with good quality and carry lots of signals.
      • TOTAL INTERNAL REFLECTION-  light ray repeatedly reflects off a boundary between 2 materials.
      • Electromagnetic waves can transmit signals using ANALOGUE or DIGITAL SIGNALS.
      • Advantages of EARTH-BASED telescopes: reduced costs to manufacture and easier to repair.
      • Advantages of SPACE-BASED  telescopes: full spectrum of Electromagnetic waves can be detected, clearer images due to NO atmospheric interference.
    • Sound
      • Vibrating objects-sound waves
      • Sound waves- Longitudinal- don't pass through vacuum.
      • Sound waves can be REFLECTED,, REFRACTED OR DIFFRACTED.
      • Frequency- measure number of cycles per s & measured in Hz. Humans- 20Hz>>20000Hz.
      • High pitched-short wavelength & high frequency. Low pitched- long wavelength & low frequency.
      • Wavelength- Distance from 1 peak to the next.
      • Ray Diagrams: compared to object, images can be- upright or inverted, MAGNIFIED, diminished, or same, laterally inverted or real or virtual
      • Flat mirror forms  a same distance image behind mirror as the object is in front of it.
    • Using Waves
      • Communication systems- radio waves, microwaves, infrared, visible light.
      • Visible light- photography.
      • Infrared radiation- anything warm e.g. remote controls.
      • Microwaves- mobile phone networks and satellite communication- atmosphere doesn't absorb it.
      • Diffraction affects how well electromagnetic waves are received. If cannot diffract, the signal isn't received clearly.
      • Long-wave radio signals have wavelengths of several Km- allows to go round hills etc
      • In a vacuum, all electromagnetic waves travel at speed of light.
        • Speed/velocity of wave- Frequency (Hz) x Wavelength (m)
      • Shorter wavelength= higher frequency. More energy
      • 1-Radiowaves. 2-Microwaves. 3- Infrared. 4-Visible light. 5-Ultraviolet. 6-X-rays. 7-Gamma rays.
    • Dangers of electromagnetic radiation
      • Microwaves are strongly absorbed by water-through skin and heats cells.
      • Infrared radiation-burns.
      • Intense visible light-damage cells in retina.
      • Ultraviolet-sunburn. Prolonged exposure- skin cancer.
      • X-rays & gamma rays-kills/damage cells or burns.
      • If ultraviolet, x-rays and gamma rays are absorbed, they ionize DNA molecules. Could MUTATE or CANCEROUS TUMOR.
      • Electromagnetic waves allow signals to travel long distances-rapidly.l
        • Microwaves communicate with satellites-not absorbed by atmosphere.
          • Signals transmitted to satellite, then transmitted from satellite to another place on earth.
      • Visible light & infrared signals travel far in OPTIC FIBRES without absorption.
      • Geostationary satellites orbit above equator at same rate earth spins to remain above in their place.
        • Uses include- telecommunication satellites.

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