Question

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. $1:4$

Answer 1

Answer: (B)

$2:1$

Answer 2

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