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NEET 2026
Exam
NEET
Year
2026
Subject
Physics
Chapter
Chapter

NEET 2026 · Physics · Chapter

An ideal electric dipole of dipole moment p is placed at the...

An ideal electric dipole of dipole moment p is placed at the origin, aligned along the positive x-axis. Two points, A
An ideal electric dipole of dipole moment p⃗\vec{p} is placed at the origin, aligned along the positive x-axis. Two points, A and B, are located on the positive y-axis at distances dd and 3d3d from the origin, respectively, as shown in the figure.

If the magnitude of the electric field at point A is E0E_0, what is the magnitude of the electric field at point B?

Options

  1. AE09\dfrac{E_0}{9}
  2. BE03\dfrac{E_0}{3}
  3. CE027\dfrac{E_0}{27}
  4. D27E027 E_0

Correct answer

C. E027\dfrac{E_0}{27}

Step-by-step solution

The electric field due to an ideal (short) dipole at a point on its equatorial axis is given by:

E=14πϵ0pr3E = \dfrac{1}{4\pi\epsilon_0} \dfrac{p}{r^3}

Thus, the magnitude of the electric field is inversely proportional to the cube of the distance from the dipole, E∝1r3E \propto \dfrac{1}{r^3}.

For point A at distance r=dr = d:

EA=14πϵ0pd3=E0E_A = \dfrac{1}{4\pi\epsilon_0} \dfrac{p}{d^3} = E_0

For point B at distance r=3dr = 3d:

EB=14πϵ0p(3d)3E_B = \dfrac{1}{4\pi\epsilon_0} \dfrac{p}{(3d)^3}

EB=127(14πϵ0pd3)E_B = \dfrac{1}{27} \left( \dfrac{1}{4\pi\epsilon_0} \dfrac{p}{d^3} \right)

EB=E027E_B = \dfrac{E_0}{27}

Answer: E027\dfrac{E_0}{27}
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