GCSE Physics P1 (OCR B711): Energy For The Home

Year 10 revision topics

  • The difference between Heat and temperature
  • Temperature is represented by colour in a thermogram hottest parts: white/yellow/red; coldest parts: black/dark blue/purple
  • Thermal energy(Heat) travels from hot to cold
  • Rate of cooling depends on the temperature difference compared to the surroundings.
  • Energy in joules (j).
  • Energy needed to change the temperature of a body depends on: mass, temperature change.
  • (HL)Specific heat capacity
  • Energy = specific heat x mass x temperature rise
  • (HL) Latent heat of vapourisation and melting - all the energy goes into changing the state from solid to liquid rather than increasing the temperature
    eg Melting ice cubes, boil water
  • Extra energy needed to melt ice but not change the temperature
    i.e. no temperature change when materials are boiling, melting or freezing
  • Ways that heat travels through conduction, convection and radiation.
  • Trapped air = good insulator.
  • Infrared radiation is reflected from a shiny surface
  • Which materials radiate energy best?
  • Sankey diagram - the arrow diagram.
  • House insulation by Cavity wall insulation, loft, double glazing, draught excluder
  • Pay-back time for different methods of reducing energy loss
  • Efficiency = useful energy output divided by total energy input
  • Conduction - transfer of kinetic energy between particles, by free electrons
  • Convection - when a liquid or gas is heated causes a change of density which results in fluid flow. Radiators
  • Radiation - infrared radiation is an electromagnetic wave and needs no medium (air)

  • What are waves and how do they behave?
  • Frequency, wavelength, amplitude, crest, trough
  • Travel in straight lines
  • Refraction (bending) at a boundary and diffraction (spreading) of waves at an 'opening'.
  • Transverse, Longitudinal waves
  • Speed = frequency x wavelength
  • Light waves - Wave or particle
  • Reflection at plane mirror and 'equal angle' law, ( i = r ).
  • Spectrum of light passing through prism.
  • Refraction of light rays passing through a rectangular glass block and prism.
  • Herschel's experiment there is an 'invisible' radiation beyond the red end of the spectrum.
  • Describe the full electromagnetic spectrum
  • The use of radio, microwave, infra-red, visible and UV waves in communication.
  • Similarities (common speed, able to travel through vacuum) and differences (properties of each related to wavelength and frequency
  • Lasers produce an intense coherent beam of light with same frequency,in phase , low divergence.
  • Laser beam in a cd player
    Communicating using waves
  • Morse Code
  • Digital v Analogue
  • Refraction of light, critical angle and the optical fibre
  • Total internal reflection
  • Using of light increased the communication speed but needs a code.
  • Laser = light amplification by stimulated emmission of radiation
  • Laser is coherent beam of light with waves have the same frequency, in phase,low divergence.
  • Cooking with infrared and microwaves (heats water in food).
  • Parts of microwave oven: waves are generated (magnetron), the wave guide and the turntable

  • Communicating with microwaves (3cm)
  • Mobile phone use microwaves.
  • Diffraction of microwaves
  • Scattering of waves by water vapour, large surfaces of water; need for high positioning of transmitter/receiver; loss of line of sight due to curvature of the earth.
  • How dangerous are mobile phones?
  • Dangers to residents near the site of a mobile phone transmitter mast
  • Bar codes
  • Infrared sensors detect body heat.
  • Using infrared signals in TV controls.
  • Analogue signals have a continuously variable value, digital signals are either on (1) or off (0).
  • Advantages of digital over analogue, problems of noise in transmission.
  • Infrared for photography and security systems.
  • Optical fibres - faster internet
    Wireless technology:
    • no external/direct connection to a telephone line needed
    • portable and convenient
    • allows access when on the move
    • but an aerial is needed to pick up the signals.
  • Repeater stations and local transmitters on high ground needed for TV (shorter wavelength) but not for radio using longer wavelength.
  • 'Long Wave' (1500m) stations could be heard across long distances due to diffraction.
  • Diffraction (ground wave) and refraction leading to total internal reflection in ionosphere (skywave) and transmission of very short wavelengths through the atmosphere to reach satellites and return to earth
  • The dangers and advantages of wireless technology.
  • DAB radio: more stations available; less interference with other broadcasts; poorer audio quality compared to FM;not all areas covered
  • What can earthquakes tell us?
  • Two types of wave, transverse and longitudinal, and relate these to P and S waves in the earth.
  • S waves being unable to travel through liquid, and why P waves (longitudinal) might travel more quickly.

  • Should we spend time in the sun?
  • Ultra-violet radiation of varying wavelength :
    1. Helps to form vitamin d in the body
    2. Overexposure leads to burning,
    3. ultimately can cause skin cancer, cataracts and premature aging
    4. Darker skin prevents penetration to lower layers.
    5. use of sun-block and sun protection factor (spf).
  • What happened to the ozone layer?
  • Role of CFCs in damaging the layer
  • Calculate how long a person can spend in the sun without burning knowing (spf) of sunscreens

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