Physics II

  1. Electric charge is conserved.
    It can be neither created nor destroyed. The total electric charge of the universe is constant.
  2. Electric charge is quantized.
    Electric charge comes in interger multiples of a fundamental charge e = 1.60 x 10-19
  3. The Electric Field is:
    the force per unit charge at a point in space. It is a vector quantity which points in the direction of the force on a positive charge at that point.

    (vector)E = (vector)F+ / q+
  4. Electric field lines are:
    a graphical mapping of the electric field produced by a configuration of electric charge.
  5. Properties of electric field lines:
    • -lines start on positive charges and end on negative charges
    • -the direction of the electric field is tangent to the field line
    • -field lines never cross since the direction of the force on a charge is unique
    • -the closer together the field lines, the stronger the electric field
    • -the number of field lines leaving or entering a charge is proportional to the magnitude of the that charge
  6. In a conductor:
    it takes very little force to strip the electrons from the atoms so that they are free to flow through the material.
  7. In an insulator:
    it takes an extremely strong electric field to cause the electrons to conduct.
  8. A semi-conductor:
    is in between the extremes of conductors and insulators
  9. Electrostatics applies when:
    the electric charges are at rest in or on the material. This produces an electric field that is constant in time.
  10. Electrostatic properties of conductors:
    • -the electric field is zero everywhere inside a charged conductor if the charges are at rest
    • -Any excess charge on a conductor resides entirely on the surface of the conductor
    • -the electric field at the outer surface of a charged conductor is perpendicular to the surface
    • -Excess charge accumulates at sharp or sharply curved points
Card Set
Physics II
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