6.2  Electric Fields

6.2.1  Point and spherical charges

Learners should be able to demonstrate and apply their knowledge and understanding of:

(a) electric fields are due to charges

(b) modelling a uniformly charged sphere as a point charge at its centre

(c) electric field lines to map electric fields

(d) electric field strength; E =.F/Q

6.2.2  Coulomb's Law

Learners should be able to demonstrate and apply their knowledge and understanding of:

(a) Coulomb’s law;      for the force between two point charges

(b) electric field strength      for a point charge

(c) similarities and differences between the gravitational field of a point mass and the electric field of a point charge

(d) the concept of electric fields as being one of a number of forms of field giving rise to a force.

6.2.3  Uniform Electric Field

Learners should be able to demonstrate and apply their knowledge and understanding of:

(a) uniform electric field strength; E= V/d

(b) parallel plate capacitor; permittivity; C ;

(c) motion of charged particles in a uniform electric field.

This is a moment when your suvat knowledge comes back.  There is a constant force applied in one direction on a charged particle in an electric field.  This means that they accelerate at a constant rate. This is exactly the same as a projectile moving in a gravitational field.

6.2.4  Electric potential and energy

Learners should be able to demonstrate and apply their knowledge and understanding of:

(a) electric potential at a point as the work done in bringing unit positive charge from infinity to the point; electric potential is zero at infinity

Don't panic about this.  It is exactly the same as the gravitational potential and energy bit but with different words!

(b) electric potential    at a distance r from a point charge; changes in electric potential

c) capacitance    for an isolated sphere Derivation expected from equation for electric potential and Q = VC.

(d) force–distance graph for a point or spherical charge; work done is area under graph

e) electric potential energy    a distance r from a point charge Q.