Flashcards
OCR P1 - Physics
Cards in this deck (27)
- 1Why is air a good insulator for a coat?Air is trapped inside the coat and doesn't let energy to transfer from warm body to cold surroundings.
- 2What is temperature and heat?Temp - measure of how hot something is
Heat - measurement of energy (J) - 3How does a block of ice melt when being heated?1. Temp rises sharply
2. It hits 0 - stops rising - stays until all ice is melted
3. Temp rises up to 100oC
4. Temp is constant while water changes from liquid to gas - 4What happens to water while boiling?Energy breaks intermolecular bonds as water molecules changes from solid to liquid.
- 5Fiberglass- Conduction and convection
- Layers of air trapped between the fibres. - 6Reflective foil on walls- Reduces radiation
- Reflects heat energy back into room - 7Foam cavity wall insulation- Reduces conduction and convection
- Traps air in foam - air is insulator - stops conduction and convection as it's stopped - 8Double glazing- Reduces conduction and convection
- Traps air between panes of glass - 9Draught excluders- Reduces conduction and convection
- As much warm air as possible is kept inside - 10Payback time?= cost of installing insulation/annual saving
- 11How does a cavity wall work?- Made of inner & outer wall separated by cavity filled with air
- Heat energy passes through wall by conduction
- Air in cavity is heated
- Heat carried wall by conduction
- Less heat loss by filling foam cavity
Heat loss by conduction is reduced
- Air trapped so convection reduced - 12What is conductionTransfer of heat energy through substance from hotter to cooler area w/o substance moving.
- Substance heated-KE increases-KE transferred bw particles & energy transferred along substance.. - 13Convection?Transfer of heat energy from hotter to cooler by particle movement.
- Liquid gets hotter-particles move faster-it expands,less dense-particles in hot region rise up-replaced by particles from coler region - 14Radiation?- Hot objects emit infra-red radiation (EM wave - can pass through vacuum w/o medium)
- Amount of radiation given out/taken depends on its surface
- Dark surfaces emit more radiation than shiny surfaces @ same temp - better absorbers than shiny @ same temp - 15Amplitude - maximum disturbance by wave Wavelength - distance b/w corresponding points on 2 successive disturbances Freq - no. waves produced in 1 sec
- 16EG wavesRadio
Microwave
Visible
Ultraviolet
X-Ray
Gamma Ray - 17What can a laser be used for?Communication, dental treatment, surgery, light shows, bar code readers.
*produces narrow intense beam of light of single colour. - 18Advantages & disadvantages of light- FAST
- SMALL LOSS OF SIGNAL
x - can't be used for wireless signalling as it doesn't diffract well. - 19Adv and Dis of Electrical signal?- Can be send along wires
x - Signal deteriorates - 20Adv and Dis of Radio waves?- Can be used for wireless signalling as waves can diffract around obstacles
x - diffraction leads to signal loss - 21How do microwaves heat things?- absorbed by water & fat molecules which causes them to heat up
- penetrate 1cm into food
- cause burns when absorbed by body tissue
- travel through glass/plastic
- reflected by shiny surfaces - 22Why are infrared rays used to cook and remote controls?- absorbed by black objects
- reflected off shiny surfaces
- used to heat surface of food - 23How do microwaves cook?- Absorbed by water and fat molecules in outside outside food layers - increasing KE of food
- Energy transferred to centre by conduction, convection - 24How do infrared waves cook?- Absorbed by particles on food surface 0 increasing KE of particles
- Energy transferred to middle by conduction/convection - 25How are microwaves lost?- large obstacles such as trees,mountains block signal - microwaves can't diffract around
- poor weather conditions
- curvature of earth
- interference b/w signal - 26Multiplexing?2+ signals sent down same optical fibre @ same time. Lets more information 2b sent in one go.
- 27Adv and dis of wireless communication?- No connection to phone land-line needed
- portable access anywhere
x aerial needed to pickup signal
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- Flashcards on OCR P1 - Physics, created by Katzz on 23/10/2014.
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- Katzz
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