5.1 Electric Fields

In order to understand what an electric field is first we must understand what we mean by a field in physics. The notion of field is described in this note in context to gravity. Just for revision, we'll restate the definition of field.

In Physics we can define "field of force as the region of the space within which any object of concern experiences a force."

Def$^{n}$: "Electric field is then a region of the space within which a charge experience a force."

The lines emanating from the charge is the representation of an electric field by means of field lines.

Def$^{n}$: Electric field strength is defined as the force acting per unit positive charge (test charge).

$$E=\frac{F}{q}$$

It is a vector quantity. Its direction is away from a positive charge and towards a negative charge. Its SI unit is newton per coulomb $(NC^{-1})$.

Convention on the direction of the field lines: The arrow or the direction for the field that we use as a convention is that in which; the unit positive charge would have moved if we were to place it on the field. Or in short, the direction of the field is the direction in which the unit positive charge moves in the field. The diagram below illustrate as follows,

Direction of field for the $(-{ve})$ charge (towards the central charge),

Direction of field for the $(+{ve})$ charge (away from the central charge),

Here's a good video on introduction to electric field well explained.