Electric field

• Electric field


  A region around a charge or conductor where the effect of electric force can be experienced by another charge
• Electric field lines

  • Imaginary lines used to show the pattern of electric field around a charge or conductor
  • They originate from positive charge
  • They terminate on negative charge
  • They are continuous
  • They do not cross or intersect each other
  • The strength of the electric field is measured by the number of the lines per unit area
  • A tangent drawn to the line shows the direction of the electric field
• For two unlike charges


  Attraction occurs
• For two like charges


  Repulsion occurs
• For two parallel unlike plates

  Attraction occurs
• For two negative plates that are not parallel


  Repulsion occurs
• Electric field intensity


  • Also called electric field strength or electric flux density or electric potential gradient
  • It is the ratio of the electric force to the test positive charge brought into the electric field
  • SI unit is N/C
• Electric field intensity obeys inverse square law
• Electric potential energy


  • The work done in bringing two charges together in an electric field
  • Noted by U or P.E
  • SI unit is Joules
• Electric potential


  • The work done per unit charge in bringing a charge from infinity to the electric field where it begins to experience the effect of the force of the field
  • Noted by V
  • SI unit is J/C or Volts (V)
• Electric potential


  V does not obey inverse square law, V = K/r
• Electric field intensity


  E = -dV/dr, the ratio of the potential to the distance
• If V is given as a function of r, then E is obtained by the differentiation of the V function
• Conversely, V = integral of E dr
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