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2013-02-20 04:44:39

physics sfsu
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  1. investiagted electricity and made serval discoveries
    ben frank
  2. proposed thatelectricity is composed of two charges
    ben frank
  3. proved lightening as a form of electricity
    ben frank
  4. two ways a neutral object reacts near a charged object
    • charged object will repel the like charge in the neutral object and attract all of opp charge
    • object will polarize with opp charge at surface
  5. polarization of a neutral object depends on
    how its charges move
  6. if the charges cannot move it is known as
  7. non metallic
    cannot conduct heat or electricity
  8. an object whose charges move easily
    conducts heat and elect
  9. charge
    quantity that can be measured
  10. most change in electrical charge are caused by
    the movement of electrons
  11. protons are located
    at the center of an atom
  12. electrons are located
    near the surface of an atom
  13. why does electricity involve the movement of electrons
    because electrons are lighter to move than protons
  14. sound that force is proportional to the amount of charge on each of the objects
  15. the direction of force is only the line connecting
    the charge and is attractive when opp charge and repel when same charge
  16. van de graff generator work
    • machine that places a large electric charge on a sphere
    • like charges move away
    • attracted to opp charge on ball and can discharge through air creating a spark
  17. these two are inverseley proportional square forces
    • gravitational
    • electric forces
  18. 3 differences between gravitational and electric force
    • grvity depends on mass electric on charge
    • gravity attracts electricity repels
    • for fundamental particles electric force is stronger
  19. electric charge creates
  20. a charge experiences forces from
    several other charges
  21. superposition principle
    electric force is the vector sum of all the forces
  22. a good way to create a uniform electric field is with
    two flat plates of opposite charge called a parallel plate capacitor
  23. because of the E field in a capacitor a charge inside it will
    move and a moving charge will be detected
  24. 3 ways electric field is considered real
    • imports a force on a charge
    • can be measured at any pount in space
    • everything about forces can be used to understand E fields
  25. why is the electric fiel within a conductor zero
    because if there wasnt there would be a force on those charges, however, since its in a conductor charges are free to move in response to those forces
  26. why does a conductor have apointy part
    more charges will accumulate there to be far from the other charges so the stronger E field will occur there
  27. how lightening is produced 4
    • Fast moving couds sweeping charges upward
    • clouds become negatuvely charged while the ground is positive
    • air is an insulator
    • E builds up, the air ionizes and becomes a conductor
  28. typical lightneing bolt transfers ___C of charge
  29. the gravity field is also known as
    a force field
  30. if we move an object against the gravity field
    if we move a charge in an E field
    • the object acquired a greater potential energy
    • we change its potential E
  31. the change in energy depends on what three things
    • the strength of the field
    • the strength of the charge
    • distance model
  32. Electrical potential is the
    potential energy per charge
  33. Electric potential
    how much PE a positive charge of 1C would have at that point
  34. Electric potential energy
    is simply the energy or work it takes to move a known charge between two locations
  35. electron volts
    an electron in an electrical field will feed a force and accelerate. It will then pick up speed and therefore increase in KE
  36. In an electric field, positive charges move
    in the direction of electric field
  37. In the electrical field, negative changes move
    in the direction of opposite electric field
  38. In electrical potential, positive charges accelerate in the direction of
    decreasing electric potential
  39. in electrical potential, negative charges accelerate in the direction of
    increasing electric potential
  40. In electrical potential, when it both has negative and positive charges the charge moves
    to the region of lower potential E
  41. While force and electric field depend inversely on distance squared...
    PE depends inversely distance
  42. net worth
    the sum off all your positives and negatives
  43. Net Force
    the vector sum of all forces acting at one point
  44. force components
    simply projections of vectors F12 & F13 onto the x and y axis
  45. 4 importances of electric field lines
    • points along the E field vector at every point
    • start at +/- charge to infinity
    • more dense where field is stronger
    • tells which way test particles would move
  46. superposition principle differences between Electric field vector and electrical potential
    • EFV at a given location is the vector sum of all electric fields at that point
    • EP at a given location is the scalar sum of the EP at that point due to all nearby charges
  47. equipotential lines
    lines that connect points of = electric potential
  48. capacitor
    two conductng plates with area A seperated by a distance
  49. an electric potential diff is established between the plates using a battery. The batter causes charges to build up on each of the plates
  50. the exact amount of charge depends o n
    how much charge can be carried in a capacitor
  51. capacitance
    define the amount of charge that builds up on a capacitor for a given potential
  52. parallel capacitor plate
    two parallel plates seperated by a distance
  53. what does and doesnt capacitance depend on
    • does:
    • ratio of quantities of charge and voltage

    • doesn't:
    • amount of charge on plates
    • potential diff between plates
  54. a flow of electric charge from one place to another
    electric current
  55. when charge flows through a closed path and returns to starting point and occurs again
    electric circuit
  56. electrons in a metal wire can only move freely if
    the wire is connected to a source of electrical energy
  57. what does a battery do
    uses chemical rxn to produce diff in electric potential between the two ends
  58. ends of battery
  59. high electric potential in a battery
    low electric potential in battery
    • +
    • -
  60. no closed path through which the electrons can flow
    open circuit
  61. electromotive force occurance
    battery disconnected from a circuit and carries no current
  62. the diff in electric potential between its terminals is referred to as
  63. the greater the current flowing through a battery the greater
    the reduction in potential diff between its terminals
  64. emf determines
    the amnt of work a battery does to move a certain amount of charge around a circuit
  65. the direction of the current in an electric circuit is the direction which
    a positive test charge would move
  66. the amount of voltage diff is called
    battery's emf
  67. EMF is not force
    Weird E is not electric field and not energy
  68. flow of positive charge
  69. current 3 importanrt details
    • have high PE when near + poles
    • they are repelled by the battery's + pole
    • move circuit to the negative pole
  70. how do insulators react to the flow of electrons compared to conductors
    insulators resist the flow more than conductors
  71. used to determine the resistance the flow of a current when a voltage diff is placed on it
  72. resisting the flow of electricity
  73. 3 parts of a simple circuit and function
    • battery-provides charges with PE
    • wire-made of a conductor
    • load-component that does something
  74. a high current flows from the positive to the - terminals of the battery
    short circuit
  75. switch that prevents short circuit
    circuit breaker
  76. anything that consumes or produces energy over time by a power associated with it