Electric Fields

Electric fields in general

  • For electricity, there are two charges: Positive and Negative.
  • The charges follow the rule: Opposites attract, Like charges repel.
  • We define the direction of an electric field as the direction a positively charged particle would take within a field.
  • Using "Lines of Force," we can see how an electric field behaves.
  • There are a few rules to apply in drawing and interpretation of these lines:
    • Field lines begin on positive and end on negative.
    • The angle they begin and end on is 90 degrees. (Must be indicated if drawn)
    • Field lines never cross.
    • Field lines that are closer together indicate a stronger field and vice versa.
    • A negative particle would go the opposite direction to the field lines.

Point Charges

  • A charged particle produces a radial electric field in the surrounding region.
  • Similar to a gravitational field, any other charges within this field will experience a force.
  • Also like a gravitational field, the strength of the field is inversely proportional to the distance away from the origin.
  • Force on a charged particle can be given by
\begin{equation} F = qE \end{equation}
  • Where:
    • $F$ is the force on the particle (N)
    • $q$ is the charge on the particle (C)
    • $E$ is the electric field strength ($Vm^{-1}$)
  • The direction of force on a charge is as follows.