physics p1

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ENERGY TRANSFER

  • Energy can be transfered or dispersed but cannot be destroyed
  • Only part of the energy is useful, the rest is wasted
  • The wasted enrgy spreads out and becomes less useful

efficiency - useful energy/total energy in (x100)

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TRANSFERING ELECTRICAL ENERGY

  • the amount of energy transfered depends on the power and time it is on
  • E=pxt
  • E= energy in kilo-watt hours (kWh)
  • p= power in kilo-watts (kW)
  • t= time in hours(h)

OR

  • E=energy transfered in joules (J)
  • p=power in watts (W)
  • t= time in seconds(s)
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WAVES

  • transverse or longitudinal
  • electromagnetic waves are transvers
  • soundwaves are longitudinal
  • mechanical waves can be either transverse or longitudinal
  • longitudinal waves show areas of refraction and compression
  • waves can be reflected, refracted and diffracted
  • waves change direction when they are refracted
  • v=fxw
  • v= speed in metres per second (m/s)
  • f= frequency in hertz (hz)
  • w= wavelength in metres (m)
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REFLECTION

  • the normal is a construction line perpendicular to the reflecting surface
  • the angle of incidence is equal to the angle or reflection
  • the image produced in a plane mirror is virtual, upright and laterally inverted
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SOUND

  • sound waves are longitudinal
  • sound waves cause vibrations detected as sound
  • pitch is determined by frequency
  • loudness is determined by amplitude
  • echos are reflections of sounds
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INFRA-RED RADIATION

  • all objects emit and absorb infra-red
  • the hotter an object the more infra-red emitted
  • dark, matt surfacers are good absorbers and emitters
  • light, shiny surfaces are poor absorbers and emmiters
  • light, shiny surfaces are good reflectors of infra-red
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HEATING AND INSULATING BUILDINGS

  • U-values measure how effective an insulator is
  • the lower the u-value the better the material
  • solar panels contain water heated by the sun; used to heat buildings and as hot water
  • specific heat capacity is energy needed to raise temp by one degree of a one kilo sample
  • E=mxcxt
  • E = energy transfered (J)
  • m = mass (kg)
  • t = temperature change (degrees)
  • c = specific heat capacity (J/kg C)
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ELECTRO-MAGNETIC WAVES

  • all types travel at the same speed through a vaccum
  • Form a continuous spectrum

Radio waves, microwaves, infra-red radiation, visible light, ultra violet, x-rays, gamma rays

  • radio waves, microwaves, infra-red and light can be used as forms of communication
  • radio waves - t.v. and radio
  • microwaves - mobiles and satellite t.v.
  • infra-red - remotes
  • visible light - photos
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RED SHIFT

  • the doopler effect is the change in wave length and frequency observed when a wave source is moving relative to an observer
  • wave source could be light or sound or microwaves
  • as it moves away wavelenght increases and frequency decreases
  • as it move towards wavelength decreases as frequency increases
  • the further a way a galaxy is, the faster it is moving, the more red-shift is detected
  • Red shift supports the 'Big bang theory'
  • cosmic microwave background radiation comes from the radiation present shortly after the universe began
  • 'Big bang theory' is only theory that supports CMBR
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