明察秋毫-金屬的熱膨脹

摘要或動機

Thermal expansion exists in our daily life. However, thermal expansion is generally
too slight to be seen by naked eyes. Therefore, in the present project, a dilatometer
was assembled to enhance better sensitivity toward thermal expansion. Hopefully
the self-assembled dilatometer could contribute to teaching purpose.The structure
of our 4^th generation dilatometer is showed below. Using an ‘L’ square to hang up
the metal stick and a rolling needle with a mirror to reflect the laser light are
the critical parts of this equipment. By using this special reflection mechanism,
the slight expansion of a metal stick caused by heat can be enlarged to a large
scale. This special mechanism is where our creativity laid. Measuring in millimeter
(mm), the measurement precision of the equipment can be extended to 0.0001 decimal.
Our dilatometer was used to measure the expansion of various metal sticks caused
by the temperature changes. Results were drawn from analysis of the data: 1) The
average relative deflection was within 1.0~1.8%; 2) The relative deviation of linear
thermal expansion coefficient was within –1.2~-4.4%.


物質熱漲冷縮的特性普遍存在於我們的生活環境中，但因其變化量相對微小，一般並不容易直接觀察，爲了進一步研究這課題，我們組裝偵測熱膨脹的儀器，並希望儀器的靈敏度高，能推廣為教學器材，經過我們不斷努力與改良，終於有了令人愉悅的成果。

自製第四代熱膨脹儀的結構如圖，設計「角尺懸吊金屬棒」與「滾針及鏡面反射」是儀器的重要部份，利用滾針旋轉及鏡面反射雷射光，加乘放大熱膨脹的微量變化，這是我們主要的創意，以公厘（mm）為單位，儀器的精確值到小數第四位。

利用自製的熱膨脹儀，探討金屬熱膨脹的影響因素。分析實驗所得數據，平均相對偏差在1.0~1.8﹪，而線膨脹係數的相對誤差約-1.2~-4.4﹪。