Module 2 : Electrostatics
Lecture 6 : Quantization Of Charge
  ELECTRIC FIELD :
  A Field, in general, is a physical quantity, which is specified at all points in space. For instance, one could talk of a temperature field, which is described by specifying the temperature all all points of space at a given time. This is an example of a scalar field, as the physical quantity involved, the temperature, is a scalar.
  The region of space around a charged object is said to be the Electric Field of the charged object. If a test charge is brought into this region, it experiences a force. The electric field at a point is defined as the force experienced by a unit positive test charge kept at that point. The direction of the electric field is the direction of the force on such a positive test charge. The electric field $\vec E$, therefore, is a vector field .
 
  where $\vec F$is the force experienced by a charge $q$.
  Coulomb's law allows us to calculate the field due to a charge $Q$. The force on a test charge $q$ due to charge $Q$ is
 
  where $\hat r$is a unit vector joining $Q$and $q$, in a direction as defined above. The electric field, which is the force per unit charge is therefore, given by
 
The unit of the electric field is newton/coulobm. The field depends only on $Q$and position vector of any point on space with respect to the position of the charge $Q$. Actual presence of a test charge is not required. The field is defined at every point in space.
1
8