ABSTRACT
The concept of field lines or lines of force is used to illustrate the properties of an electric field. However, it should be remembered that they are only aids to the imagination.
The force of attraction or repulsion between two electrically charged bodies is proportional to the magnitude of their charges and inversely proportional to the square of the distance separating them,
i.e. force / q1q2 d2
or force D k q1q2 d2
where constant k ³ 9 ð 109 in air
This is known as Coulomb’s law. Hence the force between two charged spheres in air with their centres
16 mm apart and each carrying a charge of C1.6 μC is given by:
force D k q1q2 d2
³ 9 ð 109 1.6 ð 10 62
16 ð 1032 D 90 newtons
6.2 Electric field strength Figure 6.3 shows two parallel conducting plates separated from each other by air. They are connected to opposite terminals of a battery of voltage V volts.
