OCR P1

OCR P1

1. HEATING HOUSES

   • energy is a form of heat
     • flows from a warmer body to a cold body
     • when energy flows away from a warm object to the temperature of the object decreases
   • thermogram is used to show temperature through colours
     • hottest: white and yellow and coldest: black,purple,blue
     • temperature is measured in hotness
       • on an arbitrary scale
       • thermogram used to compare temperatures o objects
       • the temperature of the body increases so does the kinetic energy
       • SHC -specific heat capacity
         • energy needed to raise the temperature of 1kg to 1.c
           • measured in j/kg.c
         • when an object is heated and its teperature increases and energy is transferred
           • energy transferred= mass * SHC* temperature change
             • SLH
               • specific latent heat
                 • energy needed to boil/melt 1kg of material it is measured in j/kg
                   • this differs for different materials
                     • when an object is heated it changes state, energy is transferred but temperature remains constant
                       • this is because the substance is needed tochange state the energy is needed tyo break the bonds that hold the molecules together this explains why the temperature doesnt change
                         • energy transferred= mass * SLH

2. practical insulation

   • double glazing
     • loft insulation
       • cavity wall insulation
         • insulation blocks
           • reduces energy by radiation
         • reduces energy loss by conduction and convection
       • reduces energy loss by conduction and convection
     • reduce energy loss by conduction
   • conduction,convection,radiation
     • conduction
       • transfers kinetic energy from one particle to another
         • mainly happens in solids
     • convection
       • is when less dense particles rise and more dense particles fall
         • happens in gasses and liquids
     • radiation
       • does not need a material to transfer energy through vacuum

3. sanky diagrams are used to measure energy efficiency

   • in the sanky diagram some energy is wasted due to the surroundings
     • building that are energy efficient are well insulated this means less energy is lost by surroundings

4. wave properties

   • amplitude is the maximum displacement of a particle from a rest position
     • crest of the wave is the highest point on a wave above the rest position
       • the trough of a wave is the lowest point on the wave below its rest position
         • the wavelength of a wave is the distance between two successive points on a wave
           • the frequency of a wave is the number of complete wave passing through one point
   • radio
     • microwave
       • infrared
         • visible
           • ultraviolet
             • x-ray
               • gamma ray
                 • increasing frequency
     • increasing wavelength
   • refraction occurs when the speed of waves decrease as the wave enters a more dense medium and increases as the wave enters a less dense medium, the frequency stays the dame but wavelength changes
     • diffraction the spreading out of a wave as it passes a gap
       • differation depends on the size off the gap. more diffraction occurs when the gap is the similar size to the wavelength but less diffraction occurs when the gap is large
         • seen through telescopes and microscopes

5. lights and lazers

   • Morse code is a digital code which consists of . and -
   • sending signals through light, microwaves, electricity or radio
     • laser light- has a single frequency in one phase and shows low divergence
       • laser light used to read cd's it does it as it reads the digital signals by different reflection
   • critical angle
     • when the angle of refraction is 90' the angle of incidence is the same as the critical angle.
       • when the angle of incidence is bigger than the critical angle it is total internal reflection
         • telephone conversations and computer data are transmitted long distance along optical fibres at the speed of light.
           • fibres are coated to improve reflection
             • endoscopes are used to see inside a body without the need for surgery

6. cooking with waves

   • infrared radition is used to cook food but can not penetrate easily through food
   • microwaves can penetrate through 1 cm of food
     • microwaves can penetrate glass or plastic but is reflected by shiny mental surfaces
       • but it can burn human tissue

7. electromagnetic spectrum

   • energy is transferred by waves
     • amount of energy depends on the frequency or the wavelength of the waves
       • high frequency has a short wavelength this means the wave is transferring more energy
       • normal ovens cook food using infrared radiation the energy is absorbed by the food and the kinetic energy of the surface of the food particles increase.
         • the rest of the food is heated up using conduction
       • microwave oven cook food using microwave radiation the fat and water molecules in the outer layer of the food vibrates more
         • it too uses conduction to heat the rest of the food
           • microwaves have a wavelength between 1mm and 30cm
             • mobile phone use longer wavelengths than microwave ovens as less energy is transferred by mobile phones
               • microwaves in communication - microwaves are used in communication over long distance
                 • the transmitter must be in the line of sight with the receiver
                   • aerials are normally situated aat the top of high buildings
                     • satellites are used for microwave communication
                       • the signal from earth is received, amplified and re transmitted back to earth
                         • large aerials can handle thousands of phone calls and tv channels at once
                           • signal strength from mobile phones can change a lot over a short distance
                             • microwave do not show diffraction
                               • adverse weather and large areas of water can scatter the signals
                                 • curvature of the earth limits the line of sight so transmitters have to be on tall buildings or close together
                             • mobile phones can interfere with sensitive equipment that is why they are banned on airplane and hospitals
                     • scientists publish their studies to allow others to check there findings

8. digital signal

   • infrared signals carry information that allow electronic and electrical devices
     • the light emitted diode -LED is sent when pressing the remote
       • digital signal is better than analogue signals as improves the signal quality also a greater choice of programmes, being able to interact with programmes and also has subtitle and guides

9. optical fibre

   • allow data to be transmitted very quickly using pulses of light