Question
Drive the expression for electric field at a point on the equatorial line of an electric dipole.
Solution
The magnitudes of the electric field due to the two charges +q and -q are given by,
The directions of E+q and E-q are as shown in the figure. The components normal to the dipole axis cancel away. The components along the dipole axis add up.
Therefore, Total electric field.
E = - (E+q + E-q) cosθ p [Negative sign shows that field is opposite to p]
At large distances (r>>a),this reduces to
