Electric Field Lines (CIE A Level Physics)

• The direction of electric fields is represented by electric field lines

Radial Fields

• A radial field spreads uniformly to or from the charge in all directions
• Around a point charge, the electric field lines are directly radially inwards or outwards:
  • If the charge is positive (+), the field lines are radially outwards
  • If the charge is negative (-), the field lines are radially inwards

The Field Lines Around Positive and Negative Point Charges

Electric field lines point away from a positive charge and point towards a negative charge

• This shares many similarities to radial gravitational field lines around a point mass
  • Since gravity is only an attractive force, the field lines will look similar to the negative point charge, whilst electric field lines can be in either direction

Uniform Electric Field

• A uniform electric field has the same electric field strength throughout the field
  • For example, the field between oppositely charged parallel plates

• This is represented by equally spaced field lines
  • This shares many similarities to uniform gravitational field lines on the surface of a planet

   

Field Lines in an Electric Field

The electric field between two parallel plates is directed from the positive to the negative plate. A uniform E field has equally spaced field lines

 

Non-Uniform Electric Field

• A non-uniform electric field has varying electric field strength throughout
• The strength of an electric field is determined by the spacing of the field lines:
  • A stronger field is represented by the field lines closer together
  • A weaker field is represented by the field lines further apart

 

Field Lines in a Non-Uniform Electric Field

A non-uniform E field has lines not spaced equally apart. Denser regions of the field have field lines closer together and less dense regions further apart