Electric field intensity due to electric dipole at equatorial or broad side position

 *“Electric field intensity due to electric dipole at equatorial or broad side position”:

*Note: please replace  2a into 2l in fig.

Consider AB is an electric dipole which is consisting by two point charges  -q  and  + q respectively of lenght 2l, thus  the electric dipole moment will be ,p = 2l×q . we are to find the electric field intensity due to this dipole in broad side on position at a distance  r  from midpoint of the dipole  at point  P  for this assuming that  the unit  positive charge  is kept at  point  P  then  intensity  produced by the + q and  -q  charges  at point p are  E1 and E2 respectively. By the vector resolution we find the rectangular component of Eare  E1cosθ and  E1sinθ·  Similarly, the vector component of  E2 are  E2cosθ and  E2sinθ·


In right ∆AOP By pythgoras
AP² = OP² + OA²
AP² = r² + l² 
AP = √r²+l² = (r² +l²)½

But AP = BP
Hence,  AP² = BP² = (r+l) 

And,  cosθ = OA/AP = l/(r²+l²)½

the electric field intensity due to point charge +q is
  
and   the electric field intensity due to point charge -q  E2  is same as   E1 but  the direction is different· 




It is clear that E1=  E2 · Thus from figure the component   E1sinθ and 
E2sinθ are equal in magnitude and 
opposite in direction· Then they are cancelation each other but the remainig components E1cosθ and
E2cosθ are in same direction· Thus 
the resultant intensity is the addition
of E1cosθ and E2cosθ·





But 2ql=p (moment of electric dipole)
    
The direction of electric field E is 'antiparallel' to the dipole axis.
If r is very large compared to 2l ( 2l), then , l² ≈ 0  
Newton/Coulomb




 

















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