Basic Electrical

Basics terms related to electrostatics 

Electrostatic Field: - The Space around the charge is always under the stress exerts a force on another charge which is placed around it. The region or space around charged body in which the influence of electrostatic force is called electrostatic field.

 Electric Flux: - The total number of lines of force or the tube of flux in any particular electric field is called electric flux. This is represented by symbol φ and unit is Coulomb.

Electric Flux Density: - electric flux density is defined as the flex passing at right angles the unit area of the surface it is represented by the symbol D and measured in coulomb per square metre.

   

Electric field intensity or electric Field strength: -it is defined as the force experienced by unit positive charge placed at any point in the electric field it is represented by the symbol E and measured in Newton per coulomb.

If a charge of q coulombs placed at point within an electric field experiences a force of F Newtons, then the electric field at that point is given by,

 

Absolute Permittivity: - The absolute permittivity, often simply called as permittivity it is defined as the ratio of electric flux density D to the electric field intensity E at any point.

It is denoted by Greek letter  and measured in units farads per metre.

                

Permittivity of free space: - permittivity of the free space is defined as it is the ratio of electric flux density in the vacuum or free space to the corresponding electric field.

It is denoted by and measured in units farad per metre the value of is less than the value of permittivity of any medium.

experimentally, its value has been derived as  

Relative permittivity: - the ratio of the electric flux density in the dielectric medium to produce in vacuum by the same electric field intensity under identical conditions is called as relative permittivity.

Or

it can be also defined as the ratio of the absolute permittivity of dielectric medium to the permittivity of the free space.

It is denoted by and it is unitless.

The relative permittivity of the air is 1( one) for all practical purpose.

The relative permittivity is nothing but the dielectric constant of the material

Relation between electric flux density and electric filed intensity:- 

The electric flux density D and electric field intensity E are related to each other as,

 

The unit of electric field intensity is Newton per Coulombs but it is also measure in volts per meter (V/m).