Electrostatics

Electrostatics

1. Bonus

   • Calculating Electric Force
     • Look out!
       • The proportionality contant "K" for Coulomb's law depends on the choice of units for charge
       • When the charge "q" is in Coulombs, the distance "r" is in meters and the force F is in newtons.
   • Summary of Formulas
     • Charges Repel
     • Charges Attract
   • Potential Energy
     • have been
       • Extended to electrical phenomena
     • when
       • A charge "q" is moved against a constant electric force for distance d, use the system: U=qEd
       • "E" is the constant electric field intensity. If the charge is released: K= 1/2mvv=qEd
       • V at a point a distance r from a charge Q is equal to the work per unit charge
       • The potential at a point in the vicinity of a number of charges is equal to the algebraic sum
       • Difference between two ponts A and B is the difference in the potentials at those points
       • The work done by an electric field in moving a charge "q" from point A to point Bcan be defined from "Work and potencial Difference"
       • The potential difference between two oppositely charged plates is equal to the product of the field intensity and the plate separation.

2. is

   • The science that treats charges at rest.
     • There are two kinds of charge
       • Negatively Charged
         • If
           • An object has an excess of electrons.
       • Positively Charged
         • If
           • Has a deficiency of electrons

3. Concepts

   • The first Law of electrostatics
     • states
       • Charges repel each other and unlike charges attract each other
   • Coulomb's Law
     • states
       • The force of attraction or repulsion between two point charges is directly proportional to the product of the two charges and inversely proportional to the separation of the two charges.
         • Bonus
           • The force F is in newtons (N)
             • only when
               • the seperation "r" is in meter
               • The charge "q" is measured in coulombs

4. The Quantity of Charge

   • Defined
     • In terms of the number of electrons, but the Coulomb (C) is better unit for later work.
       • Temporary definition
         • The Coulomb: 1C = 6.25X10 18 electrons
           • That means
             • The charge on a single electron
               • is
                 • 1 electron: e- = -1.6x10-19 C

5. Units of Charge

   • Is
     • Actually a very large unit for static electricity
       • We need to use the metric prefixes
   • The units of electric potential is in joule per coulomb

6. Electric field

   • Describe
     • The region surreounding and electric charge.
       • is determined
         • By the force a unit charge will experience at a given location
           • Distance is the same as the force on a positive charge at that point
             • Lines were postilated to give a visual picture of electric field
   • Concepts
     • Exist in a region of space in wich an electric charge will experience an electric force
       • Units
         • Newton per coulomb (N/C)
     • The resultants field intensity at a point in the vicinity of a number of charges is the vestor sum of the contributions from each charges
   • Bonus
     • Gauss's Law
       • state
         • The net number of electric field lines crossing an y closed surface in an outward direction is numerically equal to the net total charge within that surface

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