Question

The electric field due to a small electric dipole at a distance ‘r’ from the centre of dipole on axial line is ‘E’. Find the distance on the equatorial line to have sane electric field ‘E.

Answer 1

​

When a dipole AB of very small length is taken, then for a point P located at an axial distance r from the axis the electric field is given by

E=  

4πε  

0

​  

 

1

​  

 

r  

3

 

2P

​  

    ...(i)

When dipole is rotated by 90  

o

, then electric field is given by

E  

′

=  

4πε  

0

​  

 

1

​  

 

r  

3

 

P

​  

     ...(ii)

From Eqs. (i) and (ii), we get

E  

′

=  

2

E

​