The Earth is surrounded by a gravitational field. Any object within this field experiences a gravitational force. The strength of the forces can be illustrated using lines of differing lengths, while the direction can be illustrated using arrowheads pointing in the direction of the force. For gravity, the direction of the force is always towards the center of the object (in this case, the Earth). The closer something is to the Earth, the greater the magnitude of the gravitational force.
How to visualize Electric Fields?
Many of the concepts involved in dealing with electricity are analogous with those of gravity. Thus, it is relatively obvious that the magnitude of the electric force decreases as the distance from the particle increases. The direction of the force depends on the relative charges of the particles. Because of the relative nature of the interaction, an assumption that a test charge is positive must be made in order to find the direction of the force. Based on the common knowledge that similar charges repel and opposite charges attract, it can be inferred that if the source charge is positive it will repel the test charge, and that if the source charge is negative the two charges will be attracted to one another.
How to calculate Electric Fields?
Electric field is a measure of force per unit charge. In other words, it describes how much force can be expected from a level of charge from an external particle. This can be illustrated using the following equation, where E is the electric field, F is the force on the test charge and q is the test charge.
As shown in the field diagrams, the magnitude of the force varies inversely with the distance from the particle and varies directly with the strength of the source charge. This can be illustrated by simplifying the equation above using q (test charge) and Q (source charge) as the two charges in Coulomb’s Law.
What this equation shows is that the strength of the electric field is based solely on the source charge and distance. The strength of the test charge does not matter.
What are Vector Properties of an Electric Field?
The law of superimposition applies to electric fields in the same way it does with electric forces.
Because the electric field is a ratio between the electric force and the test charge, the direction of the electric field is a vector. Finding the direction is difficult, but it can be visualized quite easily. This is because the direction of the vector depends solely on the test charge. If the test charge is positive, then both the electric force and the electric field will have the same direction. If the test charge is negative, then the electric force and the electric field will have opposite directions (the field is always drawn assuming a positive test charge, while the force changes directions based on the test charge).
