Electric Fields (OCR A Level Physics)

• A charged object creates an electric field around itself
  • This is similar to the way in which magnets create magnetic fields
• An electric field can be defined as:

A region where an electric charge experiences a force

• If other charges enter the field then they will experience an electric force, attracting or repelling them from the object
  • Since force is a vector, the direction of this force depends on whether the charges are the same or opposite
• The force is either attractive or repulsive
  • Recall that opposite charges (positive and negative) charges attract each other
  • Conversely, like charges (positive and positive or negative and negative) repel each other

Electric fields are due to charges. The field around a charge gives rise to an electric force

• For a point outside a spherical conductor, the charge of the sphere may be considered to be a point charge at its centre
  • A uniform spherical conductor is one where its charge is distributed evenly

• The electric field lines around a spherical conductor are therefore identical to those around a point charge
• An example of a spherical conductor is a charged sphere
• The field lines are radial and their direction depends on the charge of the sphere
  • If the spherical conductor is positively charged, the field lines are directed away from the centre of the sphere
  • If the spherical conductor is negatively charged, the field lines are directed towards the centre of the sphere

Electric field lines around a uniform spherical conductor are identical to those on a point charge