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

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