A field provides the force to move a specific body without physically touching the body. Simple fields have two characteristics, a variable the determines the field's strength and a variable describing a property that the field needs to exert any kind of force. ("Simple" means the math used to model the fields are linear.) When physicists look closer at the causes of the fields, the math models may not be so simple. Take gravity for example.

The pull of gravity on a body on the Earth is called, weight. It is described as

w = mg

Where "w" is the force of gravity in Newtons, "m" is the mass, and "g" is the acceleration due to gravity near the Earth's surface. "g" is also called the field strength variable. The field strength variable defines the strength of the field, regardless of the nature of the body that is in the field. In this case the field strength describes the acceleration due to the pull of gravity. The "m" in the formula is the property that gravity affects and multiplies the field strength to show the over all force.

"m," mass, is the variable that gravity affects. If a body has mass then gravity affects it. The amount a body is affected is found by multiplying mass times field strength variable. But, if you examine gravity closer and create a math model to describe gravity under all circumstances then the formula is not linear any more. It is

Electric fields, on a macro scale, are also simple. The force of anything with a charge can be described with the math model of

F = qE

F	force felt on anything with a charge	Newtons [ N ]
q	charge on a body	Coulombs [ C ]
E	Electric Field Strength

When we look closer at the cause of the force we will see it is also not so simple. It follows something called Coulomb's Law.

(Coulomb's Law will be covered later in more detail.) The electric field is a vector. Which means it has magnitude and direction. The magnitude is determined by the equation F=qE. The direction is shown one of two ways.

The first way to determine the electric field's direction is by something called a vector field. The vector field is a collection of vectors that show the electric field's direction and magnitude and various locations in space. Below is what the vector field for a positively charged body would look like.

The tail of the vectors represent the location of the electric field's measurement. The length of the vector represents the electric field's strength at that location. The electric field's direction is shown by the vector's direction. There are few more rules, but they are covered in the second method, (rules 1, 2, 3, and 4.)

Showing the electric field's direction with the second method is a process called field lines. The are not as descriptive at vector fields but they are good starting point and easier to draw. Electric field lines show the path a positive particle would travel. These lines are the lines of net force. They are not vectors or scalars. Below are the electric field lines for 4 different charges. These charges are isolated from each other.

The field lines can be any length and there can be any number of them. Their length does not indicated anything because they are not vectors. They are lines with arrow tips. There are some rules to follow when drawing field lines. Electric field lines are best define by rule #1 below.

Rule 4 helps to explain the corona discharge. At the edge's and sharp points the density of fields lines increases. This means that there is more force here to be exerted on charged particles in the air. These forces will break up the air into ions.

Below is an example of a field lines for two bodies in close proximity to each other.

Vector fields can be converted to field line drawings by drawing a smooth line that connects the tails of the vectors and points in the direction of the arrows.

A body with a net charge will move in an electric field according to the way the field lines are drawn. Positive charges follow the lines and arrows. Negative charges will travel along the lines in the direction opposite the arrows.

To accelerate a particle an unbalanced force needs to be applied. This force can come from contact or from a force field. The force field can push the particle without "touching" it. One such force field is gravity. Gravity pulls everything with mass. The Moon is held in orbit because it is caught in the Earth's gravitational field. Some asteroids that pass near the Earth have their path altered when they get in the Earth's gravitational field.

The animation above shows that an abject with mass, will travel along the electric field line when placed at rest. An electric field can do the same thing to everything with a charge.

Again, this shows that a charged object will travel along the field lines. However, unlike gravitational field lines, positively charged particles follow the lines in the arrow's direction and negative charges travel in the opposite direction the arrows direction. This is because an electric field is defined as the path a positive particle would travel.