NEET 2022 Physics Electric Dipole MCQ Question

Chapter: Electric Charges and Fields

Class: 12 Physics Topic: Electric Dipole Difficulty: 🟡 Medium

✅ Ans: D — $\dfrac{1}{R^3}$

For an electric dipole:

$$p=qL$$

At a distant point $(R\gg L)$, the electric field is:

$$E\propto\frac{p}{R^3}$$

Since $p$ is constant,

$$\boxed{E\propto\frac{1}{R^3}}$$

❌ Why other options are wrong?

• A — $\dfrac{1}{R^4}$: Wrong distance dependence.
• B — $\dfrac{1}{R^6}$: Wrong power of $R$.
• C — $\dfrac{1}{R^2}$: This is the dependence for a point charge, not a dipole.
• D — $\dfrac{1}{R^3}$: ✅ Correct.

📌 NCERT Concept

For an electric dipole at a large distance:

$$E_{\text{axial}} = \frac{1}{4\pi\varepsilon_0} \frac{2p}{R^3}$$

Thus,

$$\boxed{E\propto R^{-3}}$$

🧠 NEET Trick

$$\boxed{\text{Point charge: }E\propto R^{-2}}$$ $$\boxed{\text{Dipole: }E\propto R^{-3}}$$

Final Answer: $\boxed{D}$