👉 Charge :
                    Charge is the property associated with matter due to which it produce the experience electrical and magnetic effect. 

           Current(I) = Charge(Q)/Time(t)
▪ charge is derived quantity 
     
             Q = I×t
               


We know about the Gravitational Force, similarly in the Electromagnetic Force we study the Force which is proportional to the product of their charge and inversely proportional to the square of distance between them. 

   

   👉 Coulomb's Law 

                                     F = k q₁q₂ /r²

                         

    Where q₁ & q₂ are the charges on the particle and 'r' is the distance between them and 'k' is the constant. The Force is attractive if the charges are opposites signs and is repulsive if they are same signs. We can write Coulumb's Law

  

      Where k 

                   k = 1/4πε₀

Where  ε = 8.85419 × 10^-12  C²/N-m²

              And the value of 'k'is 

          k = 9.0×10^9 N-m²/C²

👉 Distribution of Charge    

▪  Linear charge distribution  :    

                            Charge per unit lengta

                  λ = Q/ l

▪Surface charge distribution :

                             Charge per unit area

                   σ = Q/A 

▪Volumetric charge distribution :

                        Charge per unit volume 

                   ९ = Q/V

👉 Relationships between λ, σ & ९ 

       σ = dQ/dA 

          = dQ/l.dx

          = dλ/dx

      ∴ ९ = dσ/dx

  

👉 Electric Field :

  

      The space around an electric charge, where it exerts a force on another charge is an 'electric field'. 

   

              E = KQ/r²

   

   

     Where 'F' is the Force experienced by a small positive test charge q₀ due to charge q.  

        It's SI unit is NC^-1.   It is a vector quantity.  We can add charge is their is more charge responsible for electric field. Then, 

           

✦ Electric Potential Energy :

               It is defined as the amount of work done required in carrying an charge slowly either from infinity to a certain point in the electric field or vice-versa 

         U =q₁q₂/r

✦Electric Potential (V) :

          It is defined as the amount of work done required in carrying unit positive charge slowly either from infinity to a certain point in electric field or vive-versa

     

                V = U/q

                   = kQq/rq

                   = kQ/r

  q is a unit positive test chargr

▪ The relationship between electric potential energy and electric potential

              ΔV = ΔU/q

             ΔU = q ΔV

▪The relationships between work done and potential difference is

       ΔV = Wext/q

       

     Wext = q. ΔV

✦  Eqi potential Surface

                              When the value of electric potential remains same through out the surface it is known as eqi potential surface.

Tip 

      the value of work done will be zero.

          ΔW = q. ΔV      ( vf - vi = 0 in eqi potential surface)

             ΔW = q. 0 

          ΔW = 0

✦ Electric Dipole

            When the two equal in magnitude and opposite in nature changes are separated by very smaller distance it is known as electric dipole. 

        the strength of electric dipole is expressed in terms of dipole moment (p)(vector)  

       P = q × 2l

Electric dipol system in uniform electric field

       When an electric dipol is kept in an uniform electric field it will experience no force and it aligns itself parallel to electric field, so that it remains in equilibrium state and net torque acting in this situation is also zero. 

        If the dipol is slightly rotated from equilibrium position it again experience no force but, torque will be acting in this situation. 

✦ Motion of a charged particle

          F = qE

     m a = qE

          a = qE/m

 a = acceleration of charged particle

 E= electric field intensity 

 m = mass of charged body

Acceleration of +ve charged particle is always in the direction of electric field intensity 

Acceleration of –ve charged particle is opposite direction of electric field intensity 

Electrostatic Examples