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

#### Year 10 revision topics

###### P1A HEATING HOUSES
• 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
###### P1B KEEPING HOMES WARM
• 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)

###### P1C A SPECTRUM OF WAVES
• 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.
###### P1D LIGHT AND LASERS
• Describe the full electromagnetic spectrum
• RMIVUXG
• 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.
###### P1E COOKING AND COMMUNICATING USING WAVES
• 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
###### P1F DATA TRANSMISSION
• 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
###### P1G WIRELESS SIGNALS
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
###### P1H STABLE EARTH
• 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