全國中小學科展

物理

冷熱生電-熱電效應之席貝克效應(Seebeck effect)

席貝克效應〈Seebeck effect〉是熱能與電能之間的一種固態能量轉換方式,當兩種不同性質的金屬導線之端點連接形成封閉迴路時,若兩接點間有溫差,則兩接點間可測得電壓,而因單位溫差所產生的電壓差稱為席貝克係數〈Seebeck coefficient〉。由本實驗的結果發現:溫差大小、導線特性〈熱電係數〉、導線表面有無氧化層是影響席貝克效應中電壓值及席貝克係數大小的原因。溫差越大,電壓值越大。鉑〈Pt〉與其他金屬的熱電偶導線組合之熱電轉換效能為Pt-Fe > Pt-C > Pt-Al > Pt-Sn;導線的表層若有氧化層,會造成電壓在上升過程中穩定性不佳,產生高低起伏的跳動溫壓曲線,但在較高溫差時,溫壓曲線趨於穩定上升狀態。The Seebeck effect is one of thermoelectric effect. A voltage existed between two ends of different metal wires when a temperature gradient existed between the two junctions. This means the conversion of temperature differences directly into electricity. The voltage induced was called electromotive force, EMF. The EMF generated was dependent on the properties of the wires, which formed the thermocouple and the temperature difference between the junctions. This paper was to study the effect of variety of wire combinations and geomtric properties of wires in thermocouple on the Seebeck coefficient generated. The results indicated that temperature difference, wire properties, and absence or presence of oxidative layer on the surface of wires were the factors to affect the magnitude of voltage and the Seebeck coefficient. As the temperature difference between the junctions was increased, the voltage increased. The combination effiency of conversion of temperature difference into electricity of platinum was following: Pt-Fe > Pt-C > Pt-Al > Pt-Sn. The presence of oxidative layer on the surface of wires caused instability during the process of voltage increase. It made the temperature-voltage curve up and down. On the contrary, when the temperature difference was big, the temperature-voltage curve became increased stably. The temperature-voltage curve was independent of geomtric properties of wires.

彭巴效應之實驗探討

延續38 屆北市科展的研究主題繼續研究,針對實驗方法進行改良。用熱敏電阻、數位電錶、冰箱冷凍庫、不同水溫,測繪「冷卻曲線」探討彭巴效應。發現在80℃、60℃、40℃、20℃的不同水初溫中,初溫愈高的水,完成冷涷的時間愈短。由冷卻曲線觀察,發現初溫較冷的水比熱水有更明顯的過冷現象。由冷卻曲線觀察,彭巴效應非常明顯,並且可由曲線上準確量測結冰始末的時間。彭巴效應明顯,並可重覆實驗。這次的研究探討,有助於我未來在彭巴效應實驗的量測技術。可應用於一般家庭冷卻物品時,快速冷卻,節省時間。可找出結冰的經濟初溫範圍,提供往後各領域利用. Hot water freezes faster than cold water? It is surprising to most people, but it is true. It has been observed and studied in numerous experiments. I tried to set up an experiment to explore the so-called Mpemba effect. I use NTC, multi-meter and house refrigerator to construct cooling curve for water of various initial temperature. The Mpemba effect is discussed based on the cooling curve. I found that the benefit of using NTC is faster measurement, higher sensitivity and cooling process is not disturbed. By inspection of the cooling curve, the Mpemba effect is obvious and repeatable. The initial and final state of freezing process is easily determined. Cold water reveals super-cooling phenomena. Inspection of gas bubbles in freeze ice showed that cold water contains more gas than hot water.

反泡泡之形成、存活與破滅的物理特性探討

This research mainly discusses an antibubble the interesting physical phenomenon that isn’t generally noticed .We use digital video cameras to obtain the experimental results, and pick up and analyze them with the computer. The experimental result as follow: (1) The formation of an antibubble mainly relates with the surfactant ingredients.The washing liquid, which has the surfactant characteristics the thinner its concentration; the lower the success rate of the antibubble. (2) The size scope of an antibubble is situated between 0.35 cm to 0.6 cm, and the size of the antibubbles produced by different densities of washing liquids are not obviously different. (3) The interior radius of an antibubble is approximately 3/4 times of the outer radius. (4) The survival time of an antibubble is mostly within 70 seconds, some minority surpasses for 100 seconds. Its average survival time is 40.65 seconds. (5) When the temperature of water the underneath liquid is between 20℃ to 90 ℃, the higher its temperature; the lower the success rate of the antibubble. After the temperature reaches 80 ℃, the success rate of the antibubble turns into 0. Besides, the higher the temperature of water; the shorter survival time of the antibubble. (6) Antibubble die by itself can be induced two kinds of types. One is centralism death, and another one is vibration death. Vibration death is less common and rare. Its dead process lasts longer time than the general antibubble, and also has 2 to 3 times back and forth vibration. 本研究主要要探討「反泡泡」(antibubble)這個一般不被注意到的有趣物理現象。我們用數位攝影機進行實驗結果的取得,並以電腦進行擷取與分析。實驗結果為:一、 反泡泡的生成主要與界面活性劑的性質有關。洗碗精這樣具界面活性劑特性的物質濃度越稀薄,反泡泡的成功越低。二、 反泡泡的大小範圍介於0.35cm 至0.6cm,不同濃度所產生的反泡泡大小並無明顯之差異。三、 反泡泡的內半徑約為外半徑之3/4。四、 反泡泡存活時間大多在70 秒之內,僅有少數超過100 秒,平均存活時間為:40.65 秒。五、 承接液體在20℃至90℃的範圍中,隨著溫度的增加反泡泡生成成功率越下降,在80℃之後,成功率降至0。且溫度增加會使反泡泡存活的平均時間下降。六、 反泡泡自行破滅可以歸納出兩大種類型。其一為:「集中破滅」;另一為「震盪破滅」。「震盪破滅」情形較為特殊少見,其破滅過程較一般反泡泡來得更久,且有2 至3 次的來回震盪。

是誰偷了水的熱?-傳導、對流、輻射

在研究水的降溫過程中,經由探討得知散熱速率與溫度有關,而根據理化課本第五章的觀念,熱量的傳遞共分為傳導、對流及輻射三種方式,因此我們根據原理歸納出,散熱速率和溫度的關係式為R(T) = K1T+K2T4-K0(詳見P.11)。接下來,我們從散熱速率對溫度的關係曲線,找出K1、K2及K0,以探討環境條件不同時,熱量傳遞方式所產生的變化。 從實驗結果我們發現,水量越少降溫速率越快,但實際上,水量少傳導和輻射的散熱面積也較小,傳導和輻射散熱的速率隨之降低,因此散熱速率反而較低。此外,我們根據降溫速率、散熱速率和溫度的關係圖及K1、K2 的變化,探討容器厚度、空氣流速、溶液與燒杯外壁顏色不同時,散熱速率的變化,並分析在不同的條件狀態下,熱量傳遞方式的改變。最後,藉由乙醇比熱之測量,進一步驗證所推導的公式。 In the research of cooling down in temperature of water, we realized that the speed of radiation relates to temperature. According to the concept in chapter 5 of Physics, the conveyance of thermal can be divided into three ways which are Conduction, Convection, and Radiation. Therefore, we can conclude the relationship between radiation speed and temperature as R(T) = K1T+K2T4-K0 (see chapter 11). We can find K1, K2 and K0 from the relation curve of radiation speed and temperature to probe into the changes of different thermal conveyances under different environmental condition.

液晶顯示器製程及光學分析研究

了解液晶顯示器的製程及光學原理。

磁粉探傷原理探討-鐵粉在靜磁場中的受力與運動情形

磁粉探傷過程包含兩個重要的物理現象,其一是磁力線於工作瑕疵處的漏磁現象而形成邊緣磁場,其二是鐵粉顆粒受邊緣磁場的影響而向工作瑕疵處附近聚集現象分別反應出磁場在通過不同介質時所遵循的折射原哩,以及磁場分佈對鐵粉顆粒產生的磁力原理。本研究以電磁通電產生靜磁場,並利用兩電磁鐵間的氣隙來模擬工件瑕疵,因電磁鐵的磁導係數遠大於空氣之磁導係數而造成漏磁場方向機與漏磁面垂直,形成一單純的邊界條件使得邊緣磁通密度的解析解可直接利用馬克斯威爾方程式求得。我們亦導出空氣中的磁通分佈對微小的鐵粉顆粒所產生的磁力公式,發現鐵粉顆粒受靜磁力的大小與該顆粒的體積、磁通密度與磁通密度之梯度成正比,而其方向則與磁通密度之梯度一致,此結論與磁粉探傷過程中,鐵粉向工件瑕疵處聚集的現象吻合。實驗設計採用螢光粉混合鐵粉以獲致明顯的鐵粉顆粒運動軌跡,用數位錄影機紀錄後再擷取影像圖檔判讀其位置與時間之關係,進而反算鐵粉顆粒之位置與所受之靜磁力的關係,以定量的方式證實所推導的邊緣磁場分佈公式以及磁力公式。Two important physical phenomena are observed in the practice of magnetic particle inspection (MPI). The first one is that leakage flux is present in the defect area of the work-piece under inspection. The second one is that magnetic particles aggregate in the vicinity of the defect. These phenomena manifest the theory of flux refraction, which occurs in the intersection area of two different magnetic materials, and the theory of magneto-static force, which is experienced by the iron powder in a magnetic field distribution. Two electromagnets, made of cast steel, are aligned together such that the leakage flux in the air gap forms a fringing field distribution. It is this magnetic field distribution that simulates a defect area in a magnetized magnetic work-piece. Since the permeability of cast steel is far larger than that of air, the direction of the fringing field at the surface of the electromagnets is almost perpendicular to the surface. Such a simple geometry renders an analytical solution to the Maxwell’s equations. The magnetic force of the magneto-static field exerting on the magnetic particle, an iron powder in this case, can be derived by using the principle of virtual displacement. We obtain a formula of magnetic force, whose direction coincides with the gradient of the magnetic flux density and whose magnitude is proportional to the magnitude of the particle volume, the magnetic flux density and its gradient. This formula also agrees with the observation in MPI that the magnetic particles aggregate in the vicinity of the defect.

非線性振動-單擺運動方程之數值分析與研究

在我們的這主題中,以單擺為主要研究對象,利用數值方法寫成計算程式,並藉 以整理運用繪圖軟圖,描繪其運動的模式之物理意義,便是我們此主題的重點所在, 並且我們更深入於實際物理情況中,消耗力或摩擦力終將阻滯運動以迄振動不再發 生。我們一開始利用RK4 數值方法將單擺運動方程寫成Visual Basic 6.0 計算程式來解 其運動方程得到等時距之角度及角速度,再藉由Matlab5.3 繪出我們想要的圖形―角度 與時間,角速度與時間以及角速度和角度之相圖。所得的圖形中,也分為有或無阻尼, 每項中又有不同的討論,如:在已知的任何一個初始狀態下,其擺動的情況當然也有 互相之對照比較,最終得出精采的結果:且將單擺作了完整且一般性的分析。因為此 番分析研究是屬理論性,雖然實驗之佐證但我們藉由Easy Java Simulation(台灣師範大 學黃福坤教授在http://140.126.110.168/~phy50/所提供免費下載)製作動畫來驗證了我們 所得的結果是十分正確無誤【它只能得到各初始條件下之單一圖形,而我們的方法可 以將各單一相圖統整成相平面及相空間並分類】

明察秋毫-金屬的熱膨脹

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 4th 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﹪。

強電場下DNA穿透細胞膜的蒙地卡羅電腦模擬

去年暑假,我們從Newton雜誌得知,布洛貝爾博士(Dr. Gunter Blobel)由於發現了蛋白質如何在細胞之間運送,增進了人們對遺傳性疾病的了解,因而榮獲1999年的諾貝爾醫學獎。同為高分子鏈的DNA,在基因遺傳工程中常被用來在強電場的情況下穿破細胞膜,以進行基因的改造,其穿的物理機制又為何?在一場演講中,我們知道鍵振盪模型(bond-fluctuation model)可用來模擬高分子系統,因此我們想以之模擬DNA在強電場下穿透細胞膜的行為。

波動奇蹟—皂膜與皂水共振模式之研究

本研究探討肥皂膜與肥皂水的共振現象。在肥皂膜共振方面,我們以實驗探討皂膜的共 振模式與頻率的關係;並配合共振理論模型求出薄膜厚度,再與體積密度-厚度測量方法比 較。而又發現皂膜在共振時,皂膜保存時間較平常久,故進行皂膜生命期與頻率、強度的關 係。在進行肥皂膜實驗時,肥皂水滴落在喇叭上,振動出奇特的形狀,進而探討皂水共振的 特性並嘗試建立其數學模式。 ;The research is about the resonance of soap film and soapsuds. For the resonante of soap film, we tried to find out the relation between the resonant pattern and frequency by experiment; according to the resonante model, we measured the thickness of soap film, which was compaired with volume-dencity method. We found that the life-time of the resonant soap film is longer than the normal one, so we proceeded to study the relation between the life-time, frequency, and power. We observed special resonant pattern while the soapsuds fell down on the speaker. So we studied the characteristics of resonant soapsuds, trying to make the mathematical pattern of resonant soapsuds.