Question

Write the magnitude and direction of electric field intensity due to a dipole of lenfth 2a at the midpoint of the line joining the two chaeges

Answer 1

E = kq/r^2 

+.....point......- 
The distance between + and - is 2a. 
The distance between + and point is a. The distance between point and - is a. 

From the positive to the point: 
k = 9 x 10^9 
|q| = 1.6 x 10^-19 
r = a 

E = kq/r^2 
E = (9x10^9)(1.6x10^-19)/a^2 
E = (1.44 x 10^-9)/a^2 in the direction away from the point towards the negative charge. 

From the negative it would be: 
k = 9 x 10^9 
|q| = 1.6 x 10^-19 
r = a 

E = (1.44 x 10^-9)/a^2 in the direction away from the point towards the negative charge. 

If we add these two together it becomes: (3.2 x 10^-19)/a^2 towards the negative charge.