Concept of a force field as a region in which a body experiences a non-contact force.

Students should recognise that a force field can be represented as a vector, the direction of which must be determined by inspection.

Force fields arise from the interaction of mass, of static charge, and between moving charges.

Similarities and differences between gravitational and electrostatic forces:

Similarities: Both have inverse-square force laws that have many characteristics in common, eg use of field lines, use of potential concept, equipotential surfaces etc

Differences: masses always attract, but charges may attract or repel