Electric Fields

Electric Fields

1. Field patterns

   • lines wich positive test charges follow
     • field line
       • line of force
   • any two charged objects exert equal and opposite forces on each other
   • Radial field
     • E is inversely proportional to r^2
     • field strength decreases as you go further away form Q
   • Uniform field
     • E is inversely proportional to d

2. like charges repel, unlike charges attract

3. Electrons

   • electrons are responsible for charging
     • add electrons
       • gives negative charge
     • remove electrons
       • gives positive charge
   • electrical conductors
     • contain free electrons
     • must be isolated from the earth to charge
       • or electrons in conductor transfer to earth
   • insulating materials
     • don't contain free electrons

4. Electric field strength

   • force per unit charge on a positive test charged placed at a point in a field
   • unit
     • newton per coulomb
   • parallel plates
     • field lines
       • parallel to each other
       • at right angles to the plates
       • from positive to negative plate
     • field is uniform
       • electric field strength has same magnitude and direction everywhere
   • vector

5. Electric potential

   • potential gradients
     • equipotentials
       • lines of constant potential
       • lines of force of the electrical field cross the equipotential lines at right angles
     • change of potential per unit chane of distance in a given direction
   • work done per unit positive charge on a positive test mass when it is moved from infinity to a position in an electric field

6. Coulomb's Law

   • force of attraction or repulsion between two point charges in a vacuum