Electric field exists in the space around a charged body and can be detected by its effect on another charged body in the field. Every charged body is surrounded by such a field, which can be visualized as imaginary electric lines of force radiating from the object. An electric force acts on other charged bodies that enter the field, causing them to change their motion through the field. Thus, charged bodies exert a force on one another, even when not in physical contact, because of the electric fields that surround them. For example, particles with unlike charges attract one another, and those with like charges repel one another.
The strength of an electric field at any point in the field is directly related to the force it exerts on a small test charge placed at that point. The strength can be calculated by using the formula E = F/q. In this formula, E stands for the strength of the field, F for the force, and q for the size of the test charge. The direction of an electric field at any point is the same as the direction of the force on a positive test charge at that point.
