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Flashcards

Physics-P4

ellanabishop Science, B4, C4, P4 GCSE Inglês 96 flashcards

Physics-P4

Flashcards do conjunto (96)

  1. 1what do most smoke alarms contain?uranium 241 which emits alpha particles
  2. 2what do most smoke alarms contain?uranium 241 which emits alpha particles
  3. 3the alpha particles cause..air particles to ionise and the ions formed are attracted to oppositely charged electrodes in the alarm
  4. 4this results ina current flowing in the circuit and this means the alarm is working correctly
  5. 5when smoke enters the space between the two electrodesthe alpha particles are absorbed by the smoke particles and so cannot ionise the air, this causes a shorter current than normal to flow sounding the alarm
  6. 6A small amount of carbon in our atmosphere and in the bodies of animals and plants is radioactive ..carbon 14
  7. 7what do radioactive materials give out?nuclear radiation
  8. 8from..the nucleus of their atoms
  9. 9because...they are unstable and therefore they decay naturally
  10. 10how is radiation measured?by the number of nuclear decays emitted per second
  11. 11does the radioactivity of a radioactive substance decrease or increase with time?decrease
  12. 12what happens during alpha emissionan atom decays by getting rid of an alpha particle(of 2 electrons and 2 neutrons) and a new atom is formed
  13. 13name 4 ways the nucleus of the new atom is different from the original atom1.it is a different element
    2.it has 2 fewer protons and 2 fewer neutrons
    3.the atomic number has decreased by 2
    4.the mass number has decreased by 4
  14. 14Alpha particles are..good ionisers because they are relatively massive so they hit atoms hard enough to strip electrons
  15. 15REVISE CARBON DATINGREVISE DATING ROCKS
  16. 16what is ionisation?creating either a positively or negatively charged particle (ion)
  17. 17what happens during beta emission?an atom decays by changing a neutron into a proton. the high energy electron taken from the nucleus is a beta particle and a new atom is formed
  18. 18the nucleus of the new atom is different from the original one because (4 reasons)1.it is a different element
    2.it has 1 more proton and 1 fewer neutron
    3.the atomic number has increased by 1
    4.the mass number remains the same
  19. 19beta particles arefast moving electrons and theyre not good ionisers because they are very light and cannot easily strip an electron from an atom
  20. 20the nucleus of the new atom is different from the original one because (4 reasons)1.it is a different element
    2.it has 1 more proton and 1 fewer neutron
    3.the atomic number has increased by 1
    4.the mass number remains the same
  21. 21what is a half life?the time it takes for half the undecayed nuclei in a radioactive substance to decay
  22. 22if the substance has a very long half life this means..it stays active for a very long time
  23. 23during alpha decay2
    2H
  24. 24during beta decay0
    -1 B
  25. 25what is a gamma ray?an electromagnetic wave
  26. 26what is background radiation?radiation that occurs naturally in the environment and is around us all the time
  27. 27where is it most released from?radioactive substances in soil and rocks
  28. 28how can the level of background radiation vary?depending on the rocks in the area
  29. 29what else contributes to background radiation?cosmic rays
  30. 30what other un natural way causes background radiation?waste products from hospitals and industry
  31. 31what are radioactive isotopes used for?tracers in industry and hospitals to find out what is happening inside objects
  32. 323 ways they are used in industry?1.track the dispersal of waste
    2.find leaks and blockages in underground pipes
    3.find the routes of underground pipes
  33. 33A gamma source is used in tracers because..gamma can penetrate through to the surface
  34. 34the progress of material is tracked by a detector above the ground so1. if theres a leak the radioactive material will escape and be detected at the surface
    2.if there is a blockage the radioactive material will stop flowing so it cannot be detected after this point
  35. 35what is ultrasound?the name given to sound waves that have frequencies higher than 20,000 Hz, (above the human hearing range)
  36. 36what type of wave does ultrasound travel in?longitudinal wave
  37. 37what is the amplitude?the maximum disturbance caused by the wave
  38. 38what is the wavelength?the distance between two corresponding waves
  39. 39what is the frequency of a wave?the number of waves produced per second
  40. 40Name two things ultrasound can be used for1.ultrasound imaging-look inside people(scanning)
    2.breaking down kidney stones
  41. 41what is ultrasound imaging and body scans?looking inside the body, measure the speed of blood flow, check babies development before birth, build up picture of organs in body, including heart, lung, liver, and detecting gallstones and tumours, no risk to mother or baby in prenatal scanning
  42. 42how is ultrasound used when breaking down kidney stones?they can be removed without the need for painful surgery.
    Ultrasonic waves cause the kidney stones to vibrate, making them break up, they are then passed out the body in urine
  43. 43where are ultrasound waves partly reflected?at a boundary as they pass from one substance into another
  44. 44what are two main advantages ultrasound has over x-ray imaging?1.it is able to produce images of soft tissue
    2.it does not damage living cells
  45. 45what do all waves do?transfer energy from one point to another without transferring any particles
  46. 46what happens to the particles in longitudinal waves?each particle moves backwards and forwards about its normal position parallel to the direction of wave movement
  47. 47what happens to the particles in transverse waves?each particle moves up and down about its normal position at right angles to the direction of the wave movement
  48. 48what is a circuit?a complete loop that allows an electric current to flow through
  49. 49electrons flow around the circuit from the...negatively electrode to the positive electrode
  50. 50what is resistance?a measure of how hard it is to get a current through a component in a circuit at a particular voltage.
  51. 51what is resistance measured in?ohms
  52. 52give three ways a current through a circuit can be controlled1.a fixed resistor
    2.a longer piece of resistance wire
    3.a thinner piece of resistance wire
    4.a variable resistor- a resistance that can be altered
  53. 53for given resistor..current increases as voltage increases and current decreases as voltage decreases
  54. 54for fixed resistor...current decreases as voltage increases and current increases as voltage decreases
  55. 55THE LIVE WIRE ISBROWN and carries the current to the appliance at about 230 v, fuses, circuit breakers and switches are all part of the live wire circuit
  56. 56THE NEUTRAL WIREIS BLUE, completes the circuit and carries current away from the appliance, BOTTOM LEFT
  57. 57THE EARTH WIREis green and yellow and is the safety wire that stops the appliance from becoming live, LEFT HAND SIDE
  58. 58whats the difference between a fuse and a circuit breaker? and what are they both?circuit breakers can be reset but fuses have to be replaced. They are both safety devices
  59. 59what do they do?they prevent fires, injury, death, overheating by breaking the circuit of the appliance if a fault occurs
  60. 604 steps to how a fuse works1.the fuse wire gets hot and melts or breaks down
    2.the circuit is broken so no current can flow
    3.the fuse prevents the cable overheating
    4.the appliance is protected
  61. 61but what needs to be in place for this safety feature to work?the current rating needs to be just above the normal current that flows through the appliance
  62. 62all electrical appliances with outer metal cases must have anEARTH WIRE to protect the appliance and the user
  63. 63this means...the outer case of the appliance is connected to the earth pin in the plug through the earth wire
  64. 64how does this work?1.a fault in the appliance causes it to become live
    2.the circuit short circuits because the earth wire offers less resistance. the charge on the metal casing flows along the earth wire as a very large current
    3.the fuse wire melts
    4.the circuit is broken
    5.the appliance and user are protected
  65. 65all appliances with outer metal cases...have to be earthed
  66. 66the appliances with insulated outer cases need..2 wires (the earth wire is missing).
  67. 67why don't these appliances need to be earthed?because they are double insulated, it does not matter if the live part touches the case because it is insulated
  68. 68double insulated symboldouble insulated symbol
  69. 69what is an insulating material?A material containing air pockets that reduces heat loss by conduction
  70. 70how can a charge be built up between 2 objects?2 insulating materials are rubbed together
  71. 71what is this charge called?static electricity
  72. 72why does the electricity stay on the material and not move?due to the transfer of electrons
  73. 73what charge do electrons carry?negative charge
  74. 74what charges are the materials left with after static electricity has taken place and the electrons have transferred?one is left with a positive charge and on is left with a negative charge
  75. 75give 4 examples of when static electricity can occur1.rubbing a balloon against a jumper
    2.rubbing a duster against a haircomb
    3.a duster brush attracting dust making it more effective
    4.synthetic clothing sticking to the persons body
  76. 76how can you discharge an object?by earthing it
  77. 77what happens during this process?electrons are transferred from the charged object to earth
  78. 78if you become electrically charged earthing can result in you getting an....electrostatic shock
  79. 79give an example of when earthing occurs?if someone gets charged by friction between the soles of their feet and the carpet(insulator)when walking then touches a water pipe eg radiator the charge is earthed resulting in an electrostatic shock
  80. 80name some dangers that can occur with static electricityflour mills have atmospheres with extremely flammable gasses, a discharge of static electricity eg a spark can lead to an explosion so factories need to take precautions to insure no sparks are ignited
  81. 81and another one..when large quantities of charge could flow through your body to earth eg LIGHTNING
  82. 82give two examples of when static electricity is a nuisance1.can cause dust+dirt to be attracted to insulators, such as tv screens, computer monitors
    2.it can cause some fabrics to cling to your skin
  83. 83two insulating materials with the same charge willREPEL EACH OTHER
  84. 84two insulating materials of the opposite charge willATTRACT EACH OTHER
  85. 85the material that receives electrons becomes..negatively charged
  86. 86due to..excess electrons
  87. 87the material giving up electrons becomes..positively charged due to the loss of electrons
  88. 88the atoms that become charged are then called..ions
  89. 89give 3 ways the chance of receiving an electric shock can be reduced..1.ensuring appliances are correctly earthed
    2.using insulation mats effectively
    3.wearing shoes with insulating soles
  90. 90lorries that contain flammable gasses, liquids, powders need to be earthed before unloading because..friction can build up of charge which could lead to a spark which could then ignite flammable substances
  91. 91connecting an aircraft to a fuel tanker...makes sure that any charge built up on the fuel by friction (as it flows through the pipe) flows to earth making sure there is no discharge and spark to ignite the fuel
  92. 92name 3 things static electricity can be used for1.defibrillators (restarting the heart when it has stopped)
    2.dust precipitators (reducing smoke particles in chimneys)
    3.spraying (crop spraying+paint spraying a car)
  93. 93how is a defibrillator used?1.two paddles are charged and put in good electrical contact with the patients chest
    2.the defibrillator charges into the patient
    3.charge is then passed through the patient to make the heart contract
  94. 94how are dust precipitators used when cleaning chimneys?the metal plates in dust precipiators are at high voltage, there is also high voltage grids lower down the chimney that make the dust particles charged. the charged dust particles are attracted to earthed metal plates where they clump together then when heavy enough fall back down the chimney or when the plate is struck
  95. 95how is static electricity used in spray painting a car?1.the paint gun is negatively charged
    2.paint particles become negatively charged so they repel and spread out evenly
    3.the car panel that is being sprayed is positively charged
    4. paint from negatively charged paint gun is attracted to positively charged panel
  96. 96resulting in..a fine line spray so it is applied evenly, resulting in a neutral painted car panel, also meaning less paint is wasted and even the back and sides of car that would be in the shadow of the spray receive a coat of paint

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GCSE Science, B4, C4, P4 FlashCards sobre Physics-P4, criado por ellanabishop em 31-05-2013.
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ellanabishop
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