For a short dipole placed at origin $O$, the dipole moment $P$ is along $x$-axis, as shown in the figure. If…

For a short dipole placed at origin $O$, the dipole moment $P$ is along $x$-axis, as shown in the figure. If the electric potential and electric field at A are $\mathrm{V}_0$ and $\mathrm{E}_0$, respectively, then the correct combination of the electric potential and electric field, respectively, at point $B$ on the $y$-axis is given by
  1. $V_0$ and $\frac{E_0}{4}$
  2. zero and $\frac{E_0}{16}$
  3. zero and $\frac{E_0}{8}$
  4. $\frac{\mathrm{V}_0}{2}$ and $\frac{\mathrm{E}_0}{16}$

Solution

Given:
- The electric potential of \(A\) is \(V_0\)
- The electric field of \(A\) is \(E_0\).
We need to determine the electric potential and electric field at point 8.
Step El: Electric Potential of a Dipole
The electric potential \(V\) due to a short dipole at a point at distance \(r\) is:
\(V=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{p \cdot \hat{r}}{r^2}\)
On the axial line (Point A at distance \(r\)):
On the equatorial line (Point B at distance 2r):
Since the dipole potential is given by:
\(V_A=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{p}{r^2}=V_0\)
\(V=\frac{1}{4 \pi c_0} \cdot \frac{p \cos \theta}{r^2}\)
and on the equatorial line \(\theta=90^{\circ} \Rightarrow \cos 90^{\circ}=0\),
\(V_g=0\)
Thus, the electric potential at 8 is zero.
Step 2: Electric Field of a Dipole
The magnitude of the electric field at a distance \(r\) from a dipole:
On the axial line:
\(B_{\pi k u l}=\frac{1}{4 \pi c_0} \cdot \frac{2 p}{r^3}\)
Given that of \(A\) (on the axial line of \(r\)), the field is \(E_0\) :
\(E_A=E_n=\frac{1}{4 \pi \varepsilon_0} \cdot \frac{2 p}{r^1}\)
On the equatorial line:
\(E_{\text {nquatiol }}=\frac{1}{4 \pi c_0} \cdot \frac{p}{r^3}\)
At B (distance 2r):
\(E_s=\frac{1}{4 \pi c_0} \cdot \frac{p}{(2 r)^3}=\frac{1}{4 \pi c_0} \cdot \frac{p}{6 r^3}\)
Since \(E_0=\frac{1}{4 m_1} \cdot \frac{2 p}{p}\), we con express \(E_n\) in terms of \(E_0\) :
\(E_n=\frac{E_0}{16}\)
Final Answer:
- Electric potential at \(\mathrm{E = 0}\)
- Electric field ot \(\mathrm{B}=\frac{N_y}{10}\)

Asked in: JEE Main 2025 (22 Jan Shift 2)

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