Physics · chapter PYQs

Thermal Properties of Matter, on the exam screen.

2 questions from Re-NEET 2026, NEET 2020, 2 minutes, marked +4 / −1. See them with solutions.

Thermal Properties of Matter · PYQs

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Question 1 · Re-NEET 2026 · Q24 · +4 / −1
The temperature of a metallic sphere of radius $R$ is increased by a small amount $\Delta T$ . If the linear coefficient of thermal expansion of the metal is $\alpha$ , the approximate increase in the volume of the sphere is:
Answer and explanation
Answer: (3)
For small expansions the coefficient of volume expansion is $\gamma = 3\alpha$ . Hence $\Delta V = V\gamma\Delta T = \frac{4}{3}\pi R^3 \times 3\alpha \times \Delta T = 4\pi R^3\alpha\Delta T$ . Equivalently, differentiating $V = \frac{4}{3}\pi R^3$ gives $\Delta V = 4\pi R^2 \Delta R$ with $\Delta R = R\alpha\Delta T$ . NCERT Class 11, Thermal Properties of Matter.
Question 2 · NEET 2020 · Q155 · +4 / −1
The quantities of heat required to raise the temperature of two solid copper spheres of radii r $_{1}$ and r $_{2}$ (r $_{1}$ = 1.5r $_{2}$ ) through 1 K are in the ratio
Answer and explanation
Answer: (4)
The heat required to raise the temperature of a sphere is proportional to its volume, which is proportional to the cube of its radius. Given $r_1 = 1.5 r_2$ , the ratio of volumes is $\left(\frac{r_1}{r_2}\right)^3 = \left(\frac{1.5 r_2}{r_2}\right)^3 = 1.5^3 = \frac{27}{8}$ . Therefore, the ratio of the quantities of heat required is $\frac{27}{8}$ . Chapter: Thermal Properties of Matter.