Properties of Electric Charges

  Electrically charged - the amount of postive charge does not equal the
  amount of negative charge.
  
  like charges repel - opposite charges attract
  
  The origin of charge is the atom.
  
  protons have a positive charge, electrons have a negative charge.  The
  magnitude of their charges is equal.
  
  electric charge is always conserved.
  
  Electric charge is quantized.  The smallest electic charge is referred to as
  e, or 1.602x10-19 columbs (C).
  
  
Insulators and conductors
  
  Conductors allow electric charges to move freely.
  Insulators do not allow electric charges to move at all.
  Semiconductors are somewhere inbetween.
  
  Changing charge by conduction:
  
  A neagtively charged object will discharge electrons if it comes in contact
  with a positively charge object.
  
  Charging by induction:
  
  A conductor connected to the Earth is considered to be grounded.  
  
  In induction, a charged object is brought near an uncharged object without
  touching it.  The like charges repel, causing the said of the uncharged object
  closest to the charged object to become charged, and have the opposite charge.
  Thus, the objects attract each other.  This effect is known as polarization,
  not to be confused with polarized light.
  
Coulomb's law

  F = (ke |q1||q2| ) / r 2  
  
  Where F is the electic Force between 2 objects, the q's are the charges of the
  the two objects, and the r is the radius or the distance between the objects.
  
  ke is a constant, 8.99x109Nm2/C2
  
  Note: This constant, called the Coulomb Constant, is the charge of an
  electron and of a proton.  However, protons and electons have different 
  masses. 
  
  Superposition Principle
  
  If you have 3 or more charges interacting, you can treat the forces like
  vectors.
  

The Electric Field

  Strength of the electic field

  E ≡ |F|/|q0|
  
  The direction of E at a point is defined as the the direction of the electric
  Force.
  
  E = (ke |q| ) / r 2 
  
  
The Electric Field Lines 

  By convention electric field lines are drawn from positive to negative.
  The number of lines is proportional to the magnitude of the charge.
  Field lines can not cross each other. 
  
Conductors in Eletrostatic Equilibrium  
  
  The electric field is zero inside the conductor.
  
  The electric field is perpendicular to the conductor's surface.
  
  Electric fields are more dense at sharp edges of charged objects than at
  flat surfaces or round edges.
  
  Electricy is attracted to dense electric fields.  application: lightning rod.
  
  Talk about Faraday's ice-pail experiment.
  
Millikan Oil drop experiment 
 
  Two parallel metal plates and oil droplets.  The oil droplets are charged.
  
  Electricity is quickly turned on and off in the two plates, and drop of 
  charged oil are sprayed inbetween.  The oil seems to move up and down for a
  long time before finally touching the plates.

  
HW 10:
p. 513 # 1   
p. 515 # 3 
p. 516 # 19