你一定是瘋了 wrote:
不會的又不是只有我
真正的大學生也不會啊
所以我才發問啊
什麼叫真正的大學生也不會?
看唸的是什麼科系.
你以為剛剛有回答你的人, 沒念過大學?
你一定是瘋了 wrote:
α = (1/ L...(恕刪)
When we assume that the linear expansion ΔL of a metal bar of length L is proportional to the change in temperature ΔT, according to
ΔL = α L ΔT
then we only need to set a temperature scale in order to have a thermometer.
Celsius selected 0oC when the metal bar was placed in melting ice and 100oC when the bar was placed in boiling water.
For the linear thermal expansion coefficient α Celsius obtained then
L(T=100oC) - L(T=0oC) = ΔL = α L ΔT = α L (100-0) = 100α L
arravera2 wrote:
When we assume that the linear expansion ΔL of a metal bar of length L is proportional to the change in temperature ΔT, according to
ΔL = α L ΔT
then we only need to set a temperature scale in order to have a thermometer.
Celsius selected 0oC when the metal bar was placed in melting ice and 100oC when the bar was placed in boiling water.
For the linear thermal expansion coefficient α Celsius obtained then
L(T=100oC) - L(T=0oC) = ΔL = α L ΔT = α L (100-0) = 100α L
Come on.
Do you really expect him to read ?
上面是線膨脹公式
L是膨脹後的長度
L0是膨脹前的長度
α是膨脹係數，每個不同的物質都有它的膨脹係數
ΔT是溫度差
例子:
假設有一根黃金材質的線，原長30cm，
它的線膨脹係數在20度C時是14*10^-6
然後你加熱到100度C，那麼ΔT就等於100-20=80
代入公式
L=30*(1+14*10^-6*80)=30*(1+0.00112)=30.0336
你可以很明顯的看出αΔT就是膨脹後增加的長度
而且其實跟原長比例差很多(我指增加量)
所以固體的熱膨脹不會太明顯
而面膨脹公式L=L0(1+βΔT)
而體膨脹公式L=L0(1+γΔT)
跟線膨脹的應用是一樣的
而因為膨脹係數很小，所以我們會用β=2α，γ=3α來近似
來源:雅虎
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