RE-NEET 2026 Physics Volume Expansion MCQ Question

✅ Ans: 2 → $6\pi R^3\alpha\Delta T$

Key Concept: For isotropic expansion,

$$\beta=3\alpha$$

Initial volume:

$$V=\frac43\pi R^3$$

Increase in volume:

$$\Delta V=\beta V\Delta T$$ $$=3\alpha\left(\frac43\pi R^3\right)\Delta T$$ $$\boxed{\Delta V=4\pi R^3\alpha\Delta T}$$

⚠️ Correction: The screenshot's marked answer C ($6\pi R^3\alpha\Delta T$) is incorrect. The correct answer is B → $4\pi R^3\alpha\Delta T$.

❌ Options

• A: $3\pi R^3\alpha\Delta T$ ❌ — wrong coefficient
• B: $4\pi R^3\alpha\Delta T$ ✅
• C: $6\pi R^3\alpha\Delta T$ ❌ — incorrect use of expansion relation
• D: $2\pi R^3\alpha\Delta T$ ❌ — wrong coefficient

📌 NCERT: “For an isotropic solid, the coefficient of volume expansion is three times the coefficient of linear expansion.”

🧠 NEET Trick: $\boxed{\beta=3\alpha}$ → sphere volume × $3\alpha\Delta T$.