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2018-1-4-熱膨脹
- 3. 線膨脹Linear Expansion
實驗的結果:長度增加量 ΔL 與原始長度 L0
及溫差 ΔT 成 正比
T0
L0
L
T
ΔL=?
𝛥𝐿
𝐿0 ⋅ 𝛥𝑇
= 定值 線膨脹係數𝜶
L0
L
𝛥𝐿 = 𝛼 ⋅ (𝐿0 ⋅ 𝛥𝑇)
𝐿 − 𝐿0 = 𝐿0 ⋅ 𝛼 ⋅ 𝛥𝑇
𝐿 = 𝐿0(1 + 𝛼 ⋅ 𝛥𝑇)
物質
線膨脹係數
α( 10-6 oC-1)
鋅 30.2
鉛 28.9
銅 16.5
鐵 11.8
普通玻璃 9.0
合成石英 0.5
3
- 4. 面膨脹與體膨脹
4
面膨脹
T0
T
A0
A
𝐴 ≈ 𝐴0(1 + 2𝛼 ⋅ 𝛥𝑇)
𝑥 = 𝑥0(1 + 𝛼 ⋅ 𝛥𝑇)
𝑦 = 𝑦0(1 + 𝛼 ⋅ 𝛥𝑇)
𝐴0 = 𝑥0 ⋅ 𝑦0
𝐴 = 𝑥 ⋅ 𝑦
𝐴 = 𝑥0(1 + 𝛼 ⋅ 𝛥𝑇) ⋅ 𝑦0(1 + 𝛼 ⋅ 𝛥𝑇)
𝐴 = 𝑥0 𝑦0 ⋅ 1 + 𝛼 ⋅ 𝛥𝑇 2
𝐴 = 𝑥0 𝑦0 ⋅ 1 + 2𝛼 ⋅ 𝛥𝑇 + 𝛼2 ⋅ 𝛥𝑇2
可忽略
𝐴 ≈ 𝐴0(1 + 𝛽 ⋅ 𝛥𝑇)
面膨脹係數 𝛽 = 2𝜶
- 5. 面膨脹與體膨脹
5
面膨脹
T0
T
A0
A
𝑥 = 𝑥0(1 + 𝛼 ⋅ 𝛥𝑇)
𝑦 = 𝑦0(1 + 𝛼 ⋅ 𝛥𝑇)
𝐴0 = 𝑥0 ⋅ 𝑦0
𝐴 = 𝑥 ⋅ 𝑦
𝐴 ≈ 𝐴0(1 + 𝛽 ⋅ 𝛥𝑇)
面膨脹係數 𝛽 = 2𝜶
體膨脹
𝑥 = 𝑥0(1 + 𝛼 ⋅ 𝛥𝑇)
𝑦 = 𝑦0(1 + 𝛼 ⋅ 𝛥𝑇)
𝑉0 = 𝑥0 ⋅ 𝑦0 ⋅ 𝑧0
𝑉 = 𝑥 ⋅ 𝑦 ⋅ 𝑧
𝑉 ≈ 𝑉0(1 + 𝛾 ⋅ 𝛥𝑇)
體膨脹係數 𝛾 = 3𝜶
𝑧 = 𝑧0(1 + 𝛼 ⋅ 𝛥𝑇)