question_answer

The ratio of electric fields on the axis and at equator of an electric dipole will be :             

A)  1 : 1                                      

B)  2 : 1

C)  4 : 1                                      

D)  1 : 4

Correct Answer: B

Solution :

                The electric field on the axis of a dipole of length small compared to point where electric field is to be determined is \[{{E}_{A}}=\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{2p}{{{r}^{3}}}\]                       ...(i)  where p is electric dipole moment. Intensity at a point on the equatorial line of a dipole is \[{{E}_{E}}=\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{p}{{{r}^{3}}}N/C\]                     ?.. (ii) From Eqs. (i) and (ii), we get                 \[\frac{{{E}_{A}}}{{{E}_{E}}}=\frac{2p}{{{r}^{3}}}\times \frac{{{r}^{3}}}{p}=\frac{2}{1}\]