Vidaara.orgClass 11 · Physics
CodeVID-P11-10-TTE-01
Temperature & Thermal Expansion — Assignment
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
The SI unit of the coefficient of linear expansion is:
- A.$\text{m}$
- B.$\text{K}$
- C.$\text{K}^{-1}$
- D.$\text{m}\,\text{K}^{-1}$
2.
Absolute zero on the Celsius scale is:
- A.$0\,^\circ$C
- B.$273\,^\circ$C
- C.$-273.15\,^\circ$C
- D.$-100\,^\circ$C
3.
The ratio $\alpha:\beta:\gamma$ for an isotropic solid is:
- A.$1:1:1$
- B.$1:2:3$
- C.$3:2:1$
- D.$1:3:2$
4.
Between $0\,^\circ$C and $4\,^\circ$C, water on heating:
- A.expands
- B.contracts
- C.does not change volume
- D.boils
5.
A change of $100\,^\circ$C equals a change of:
- A.$100$ K
- B.$180$ K
- C.$273$ K
- D.$212$ K
Section B — Short Answer (2 marks)
3 × 2 = 6 marks
6.
Distinguish between heat and temperature.
7.
Convert $-40\,^\circ$C to the Fahrenheit scale.
8.
Why are gaps left between rails in a railway track?
Section C — Short Answer (3 marks)
2 × 3 = 6 marks
9.
Show that for an isotropic solid $\gamma=3\alpha$.
10.
An aluminium rod 2 m long expands by 1.5 mm when heated through $30\,^\circ$C. Find $\alpha$.
Section D — Long Answer (5 marks)
1 × 5 = 5 marks
11.
Explain the anomalous expansion of water and its importance for aquatic life. State the temperature of maximum density and describe how a pond freezes in winter.
Answer Key
Section A — Multiple Choice Questions
- (C) $\text{K}^{-1}$
- (C) $-273.15\,^\circ$C
- (B) $1:2:3$
- (B) contracts
- (A) $100$ K
Section B — Short Answer (2 marks)
- Temperature measures the degree of hotness (average molecular KE); heat is the energy transferred between bodies due to a temperature difference.
- $F=\frac{9}{5}(-40)+32=-72+32=-40\,^\circ$F.
- To allow the rails to expand in summer ($\Delta L=\alpha L\,\Delta T$) without buckling or bending.
Section C — Short Answer (3 marks)
- $V=L^3$, so $V+\Delta V=(L+\alpha L\,\Delta T)^3=L^3(1+\alpha\,\Delta T)^3\approx L^3(1+3\alpha\,\Delta T)$; hence $\Delta V=3\alpha V\,\Delta T$ and $\gamma=3\alpha$.
- $\alpha=\frac{\Delta L}{L\,\Delta T}=\frac{1.5\times10^{-3}}{2\times30}=2.5\times10^{-5}\ \text{K}^{-1}$.
Section D — Long Answer (5 marks)
- Between $0\,^\circ$C and $4\,^\circ$C water contracts on heating, so it is densest at $4\,^\circ$C. As a pond cools, water at $4\,^\circ$C (densest) sinks to the bottom while colder, lighter water rises and freezes on top. Ice insulates the water below, which stays at about $4\,^\circ$C, so fish and aquatic life survive the winter.
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