Electric field and Electric line of force : defination, explanation

                      Electric field 

When an electric charge is placed at a point the property of space around the charge get modified the modified space around the charge is called as electric field. 
   There are other examples in physics where the properties of space get modified due to presence of a body (called source). The modified space in those cases is also stated in terms of field 
 1. Presence of mass of certain point produces a field, known as gravitational field , around it. 
2. Presence of magnetic pole at a point produce a field, known as magnetic field, around it. 

Origin of force between two sources 

      Force between two sources arises due to the interaction of two fields should be of similar nature. If we place two electric charge at two points, they will produce their individual electric fields around themselves. 
    These two fields shall interact with each other to produce force called Coulomb's force. If there is only one charge, it will have its own electric field. It will not experience any forces since there is no second field to interact with it. 
      For the production of force, the two fields should be of similar nature. If we have a charge' q 'and a mass 'm '. There is the presence of an electric field and a gravitational field, but there is no force between the two. 

Electric field definition 

The region or space upto which the influence of electric charge realise is called Electric field. 
Mathematically - The electric field at a point in the space is defined as force per unit charge or force per unit test charge
* Test charge means the  electric charge having unit charge. 
Electric field

Here we can write  E= F/q
            Here  q = test charge (charge having unit magnitude) 
                      F= Electrstatic force or 
                                        Coulomb force 
Electric field -
Electric field

Unit of electric field -N/C

                  Electric line of force 

Definition -Electric line of force are the imaginary line, draw from the positive chrge to the negative charge. 
Electric line of force

  • The electric field start at positive charge and end at negative charge. 
  • If we draw a tangent at any point on the electric field line it gives the direction of electric field at that point. 
  • For positive charge it is outward and for negative charge it is inward.
  • Tow electric field line never intersect with each other. Because if they intersect then at the point of intersection it gives two directions of electric field which is not possible. 
  • Electric field line can not pass through the conductor. So electric field inside the conductor is zero. 

   Electric field intensity due to point charge 

Consider a point charge +q placed at point O. Let we have to calculate the electric field at a point P. Which is at a distance r from O. Let a test charge is placed at point P.  
Then the force 
Electrostatic force

Electric field = F/q
                           Electric field
That is the magnitude of electric field. 

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