Electric Field

Electric Field

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Introduction : In previous topic we have studied about forces on charge. There exist an electrostatic force of attraction or repulsion. This forces is associated with some parameters called as electric field and electric field lines which is analogous to magnetic field and magnetic field lines. This electric field defines the characteristics of the charges which is at rest. In this topic we are going to study electric field.

Electric field : When there is a charge at rest , there exist an electric field around it. If a charge Q is placed at a point in space then  their exist a region around it having  a property that when a test charge (charge with very small or negligible magnitude)is brought in this region, it experiences a force according to coulombs law. This region around a charged object in which coulomb force is experienced by another charge is called electric field. The magnitude of this field depends on force experienced by the test charge and the magnitude of charge. Thus Electric field can also be defined as the force experienced per unit charge.

Mathematically,

E = F /q ------(1)

where,

F = force experienced 

E = electric field 

q = charge

Consider a system of two charge Q and q seperated by a distance r then, the coulomb's force is given by ,

F = Q q / 4πε₀r² -----(2)

from (1) and (2)

E = Q  / 4πε₀r² -----(3)

Equation (3) gives expression for electric field.

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Electric field due to a point charge

E = Q  / 4πε₀r² 

In the given diagram A charge -Q is placed at a point   on a sphere hence it develops an electric field around it .The magnitude of electric field around a point charge -Q at a distance r is same at all the point on the sphere. The direction of electric field is along the radius of the sphere, pointing toward the center as the charge is negative.

Note: 1)Electric field exist around a charge irrespective of the presence of other charge.

2) Electric field is a  vector quantity

 SI unit of electric field is,

N/C = Newton per coulomb

OR

V/m =  Volt per meter

Dimensions [E]

[E] = [ L¹ M¹  T^-3  I^-1]

│<<<Coulomb's law│    │Electrical flux>>>│

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