Electric Fields

Slide 1

• Electric Fields
• Electric fields are created by electric charges. If a charged particle ventures into this electric field, then it will experience a force. The magnitude of which depends of the charge and strength of the electric field.
• Electric Field Strength, E, at a point is the force experienced per unit charge exerted on a positive charge placed at that point.
• Electric field patterns can be mapped out
• using electric field lines. The direction of the field at a point in space shows the direction of the force
• experienced by a small positive charge. Hence electric fields point away from positively charged objects
• and towards negatively charged objects.
• A uniform electric field is created when two oppositely charged parallel plates mean the electric field
• strength is constant and the electric field pattern has parallel lines which are evenly spaced. The p.d.
• between the plates is V and they are separated by distance d. A positive charge Q moves across.
• E is electric field strength.
• Work done on charge = energy transformed
• (for parallel plates ONLY)

Slide 2

• Coulomb’s Law states two point charges exert an electrical force on each other that is directly
• proportional to the product of the charges and inversely proportional to the square of separation
• between them.
• i.e.
• Comparing electric and gravitational fields, the similarities are:
• - Both electric and gravitational fields are to do with ‘action at a distance’
• - Field strengths follow an inverse square law with distance.
• - A point mass and point charge both produce radial fields
• - Field strength is defined as force per unit mass or positive charge.
• The differences are
• - Electric field is created by charge, whilst a gravitational field by mass.
• - Electric fields can be attractive or repulsive. Gravitational fields are always attractive.