# The Electric Field

• The electric field is simply a label attached to every point in space. It gives the magnitude and direction of the electric force which a charge of +1 Coulomb would experience at that point.
• One can measure the electric field directly by observing the electric force on a little test charge at different locations.
• The electric field is defined as
```                      electric force      Newtons
E  =  -------------      -------
charge          Coulomb
```
• One can calculate the electric field due to a point charge:
```                              charge
E  =  k * ------------
(distance)^2
```
• The electric field lines point away from a positive charge (because a charge of +1 C would move away from it) and toward a negative charge (because a charge of +1 C would move toward it).
• The electric fields due to several particles simply add together in a vector sense (component by component).
• One can calculate the electric field between two uniformly charged plates (which are much larger than the distance between them):
```                           Q
E  =  --------
eps * A
```
where
```              Q   =   magnitude of the charge on each plate
eps =   permittivity of free space
=   8.854 x 10^(-12)    C^/N-m^2
A   =   area of each plate
```
The electric field between parallel plates doesn't depend on the distance away from either plate.

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