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干燥的季節里，脫毛衣時頭發根根豎起；晚上，在黑暗中還會看到衣服摩擦產生的小火花……相信每個人都曾和“靜電”過過招。那么，有趣的靜電現象背后有著怎樣的科學原理呢？你知道生活中哪些電器設備是受靜電現象啟發而發明的嗎？
By Corey Binns
穆陽 選譯
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We’ve all have experienced static electricity in one way or another. Those unexpected little shocks we get when we touch a doorknob or some other metallic object, the balloons that stick to the wall after being rubbed in the head, or hair itself standing straight when it comes close, all are produced by static electricity. Most of the time it is produced when two objects come in contact or are rubbed together. What is Static Electricity? All materials are made up of molecules, and all molecules have tiny atoms, with positively charged protons, neutral neutrons, and negatively charged electrons. Most of the time an atom is neutral with the same number of protons and electrons. When an atom’s proton and electron numbers are uneven, the electron dance begins. If you place two different materials next to each other, electrons will start jumping from one material to the other. Static electricity is generated when any material gains or loses electrons and becomes positively (when it loses electrons) or negatively charged (when it gains electrons). The accumulated charges are what’s called static electricity. Conductive materials like metals and carbon hold onto their electrons tightly, whereas insulating materials, such as plastic, can be charged by friction because they easily gain or lose electrons. In 600 BC, the Greek philosopher Thales[1] observed that some combinations of materials have more potential to make sparks fly than others. Materials can be catalogued in order of their tendency to become charged, from positive to negative. The lower an item sits on the list, the more likely it will attract more electrons and become negatively charged. Rubbing objects far from each other on the list creates a bigger charge than objects closer together. For example, polishing a glass plate with a silk scarf electrifies the scarf so that it acts like a magnet. When you stride across a wool carpet in leather shoes, your shoes pick up extra electrons from the carpet with each step. By the time you lift your foot up off the ground, the electrons will have spread around your entire body, giving you a negative charge. The next time you put your foot on the carpet, your shoe doesn’t have any extra electrons, but your head might. So more electrons make the leap to your foot. “As you keep walking across the floor, you become full of electrons,” said Todd Hubing, from the Electromagnetic Compatibility Laboratory at the University of Missouri-Rolla. “Eventually more electrons don’t want to come up on you because you’re so charged up. You end up with a high voltage, about 20,000 to 25,000 volts.” That’s serious power at your fingertips, considering a normal electrical outlet on the wall is only around 100 volts[2] of electricity. Practical Uses of Static Charges Dust removal: There are some appliances that can eliminate dust from the air, like air purifiers. They use static electricity to alter the charges in the dust particles so that they stick to a filter of the purifier that has an opposite charge as that of the dust (opposite charges attract each other). This effect is also used in industrial smokestacks to reduce the pollution that they generate. The effect is basically the same as the home air purifier. Photocopy: Copy machines use static electricity to make ink get attracted to the areas where we need the information copied. It uses the charges to apply the ink only in the areas where the paper to be copied is darker (usually this means text or other information) and not where the paper is white, this process is called xerography. Car painting: To make sure a car’s paint is uniform and that it will resist the high speeds and weather to protect the car’s metal interior, it is applied with a static charge. The metal body of the car is submerged in a substance that charges it positively, and the paint is charged negatively. This process ensures a uniform layer of paint, since when there is enough negative paint in the car the extra will be repelled by the paint already in the car. It also ensures that the paint won’t fall off.
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我們每個人都已通過各種不同的途徑體驗過靜電。我們接觸到門把手或其他金屬物體時身上感到的那些不期而至的小電擊，與頭發摩擦后粘在墻上的氣球，或是靜電在附近時豎起的發絲，這些都是因靜電產生的。大多數情況下，靜電是在兩個物體接觸或互相摩擦時產生的。 什么是靜電？ 所有的物質都是由分子構成的，而所有的分子內都有微小的原子、帶正電荷的質子、中性的中子和帶負電荷的電子。大多數情況下，由于質子和電子的數量相等，原子呈中性。而當一個原子的質子和電子數不均衡時，電子便開始跳躍起來。如果你將兩種不同的材料放在一起，電子就會開始從一種材料跳到另外一種上。 靜電的產生是由于任何一種材料因得到或失去電子而變得帶有正電荷（失去電子的情況下）或帶有負電荷（得到電子的情況下）。這些累積的電荷就是所謂的靜電。像金屬和碳這樣的傳導性材料能把它們的電子緊緊抓住，而絕緣性的材料，如塑料，則可以通過摩擦帶電，因為此類材料很容易得到或失去電子。 公元前600年，希臘哲學家泰利斯觀察到一些材料的（特定）組合比其他組合更能產生四散的火花。各種材料按照從易帶電到不易帶電可以排列為從正到負的順序。一件物品在這個表單的位次越靠下，就越容易吸引更多的電子而帶負電。摩擦兩個在表單上位列較遠的物品，能比摩擦離得較近的物品產生出更大的電荷。例如，用一條絲巾擦一塊玻璃盤子就會使絲巾帶電，它可以起到磁鐵的作用。 當你穿著皮鞋大步走過一塊羊毛地毯時，每走一步，皮鞋就會從地毯上獲得多余的電子。當你的腳向上抬起離開地面時，這些電子就會流散到你全身，令你帶負電。接下來當你把腳又踩在地毯上時，鞋子上就不會再有多余的電子了，但你的頭上可能會有。所以更多的電子就會跳向你的腳。 “當你繼續走過地板時，全身就會充滿電子，”密蘇里大學羅拉分校電磁兼容實驗室的托德?哈兵說。“到最后不會再有電子附上你的身體，因為你已經被充滿了電。最后你會帶有高電壓，大約兩萬到兩萬五千伏。”這時你手上可帶有不小的電力呢，想想墻上的一個普通插座才有大概一百伏的電。 靜電的應用 吸塵器：有些電器能夠去除空氣中的灰塵，例如空氣凈化器。這些電器利用靜電來改變灰塵顆粒中的電荷（極性），使它們附著在凈化器上一塊與灰塵顆粒所帶電荷相反的過濾器上（極性相反的電荷相吸）。這種效應還被應用在工業煙囪上，以減少其產生的污染。其作用原理與家用的空氣凈化器基本上是相同的。 影印：影印機利用靜電使油墨附著在我們需要復印信息的區域。它利用電荷將油墨僅附著在要復印紙張較深色的區域（通常較深色的區域就是文字或其他信息），而不是附著在紙的白色區域，這個過程就叫做靜電復印。 汽車噴漆：為了保證汽車漆層的均勻一致，而且能夠抵御高速行駛和各種天氣條件的危害以保護汽車的金屬內層，噴漆應用了靜電原理。汽車的金屬車身被覆上一種帶正電荷的物質，而涂料則帶有負電荷。 這一過程確保了漆層的均勻統一，因為當車上已有足夠負電荷的油漆時，多余的漆就會被車身上已有的漆排斥。它同時保證了漆不會脫落。 （來源：英語學習雜志） |
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Vocabulary: 1. Thales: 泰利斯（624?—546? BC），古希臘哲學家、數學家、天文學家，“希臘七賢”之一，認為水為萬物本原，相傳曾準確預測過公元前585年的一次日蝕。 2. 目前世界各國室內用電所使用的電壓大體有兩種，分別為100V—130V，與220—240V兩個類型，采用前者的國家有日本、美國、加拿大等；而我國和許多歐洲國家則采用的是220—240V的電壓。 |
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