8.3.A—Describe the electric field produced by a charged object or configuration of point charges

Describe the electric field produced by a charged object or configuration of point charges.

• Electric fields may originate from charged objects.
• The electric field at a given point is the ratio of the electric force exerted on a test charge at the point to the charge of the test charge. Relevant equation:  =EF q E
  • i. A test charge is a point charge of small enough magnitude such that its presence does not significantly affect an electric field in its vicinity.
  • ii. An electric field points away from isolated positive charges and toward isolated negative charges.
  • iii. The electric force exerted on a positive test charge by an electric field is in the same direction as the electric field.
• The electric field is a vector quantity and can be represented in space using vector field maps.
  • i. The net electric field at a given location is the vector sum of individual electric fields created by nearby charged objects.
  • ii. Electric field maps use vectors to depict the magnitude and direction of the electric field at many locations within a given region.
  • iii. Electric field line diagrams are simplified models of electric field maps and can be used to determine the relative magnitude and direction of the electric field at any position in the diagram.