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郭德綱鐵蟲 (初入文壇)
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[求助]
物理學(xué)大師：微波爐的利與弊？
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多年前俺看到某人在某篇文章，現(xiàn)在在微博上中說“微波是通過電場變化讓食品中的水分子高速旋轉(zhuǎn)、相互摩擦產(chǎn)生熱量來加熱食品的” 我當(dāng)時給某人發(fā)過email指出過，摩擦是宏觀現(xiàn)象，分子這樣的微觀粒子，沒有一個“表面”可以讓他們“相互摩擦”，熱也是宏觀想象，一個分子是沒有辦法產(chǎn)生出來“熱量”或者變熱的。但是某人非常堅定的認(rèn)為是我物理不到家，分子是可以摩擦的，并給我一些國外的網(wǎng)頁論證說分子必須要摩擦，微波爐才能加熱。 他說除非我找到一個外國的物理學(xué)家告訴他說他是錯的他才信，這個對我的人際關(guān)系挑戰(zhàn)過于巨大，所以我也就放棄了說服他。 事隔多年，鐵錘飛去又飛來，都快忘了這個事了，今天在果殼網(wǎng)上看到那個路由器輻射的帖子，又想起來這樁往事。到底現(xiàn)在關(guān)于微波爐加熱原理的的科學(xué)權(quán)威的解釋是啥？ 發(fā)帖子前還去看了一眼百度百科的微波爐詞條，說得和我的理解差不多，但是也很不嚴(yán)謹(jǐn)，說什么“產(chǎn)生了類似摩擦的現(xiàn)象，使水溫升高“，這樣的解釋顯然是滿足不了我也說服不了某人的。 微波爐到底是怎么工作的？有何利弊？ 現(xiàn)在微博上炒作很厲害，又說起微波爐容易引起癌癥云云。無人能解。 |
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heyang_lu
鐵蟲 (小有名氣)
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5樓2012-11-05 22:15:20
heyang_lu
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【答案】應(yīng)助回帖
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感謝參與，應(yīng)助指數(shù) +1
華麗的飄過: 金幣+3, 3q 2012-11-04 13:16:51
感謝參與，應(yīng)助指數(shù) +1
華麗的飄過: 金幣+3, 3q 2012-11-04 13:16:51
| 水分子存在于大多數(shù)食物中。水分子的“兩端”分別帶有正電荷和負(fù)電荷。電場會使水分子的正電荷端指向同一個方向。微波電場的正、負(fù)極方向每秒鐘轉(zhuǎn)換49億次，水分子也不停地隨之轉(zhuǎn)換方向。隨著水分子不斷轉(zhuǎn)向，彼此發(fā)生碰撞，相互摩擦進(jìn)而產(chǎn)生熱量。陶瓷和玻璃容器中不含水分，因而不會發(fā)熱，但變熱的食物會通過熱傳導(dǎo)使它們變熱。 |
2樓2012-11-04 12:19:53
heyang_lu
鐵蟲 (小有名氣)
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【答案】應(yīng)助回帖
★ ★ ★
華麗的飄過: 金幣+3, 3q 2012-11-04 13:17:00
華麗的飄過: 金幣+3, 3q 2012-11-04 13:17:00
|
來自http://en.wikipedia.org/wiki/Microwave_oven Principles For more details on this topic, see dielectric heating. A modern microwave oven A microwave oven works by passing non-ionizing microwave radiation, usually at a frequency of 2.45 gigahertz (GHz)—a wavelength of 122 millimetres (4.80 in)—through the food. Microwave radiation is between common radio and infrared frequencies. Water, fat, and other substances in the food absorb energy from the microwaves in a process called dielectric heating. Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, when dispersed as molecular vibration in solids and liquids (i.e., as both potential energy and kinetic energy of atoms), is heat. Microwave heating is more efficient on liquid water than on frozen water, where the movement of molecules is more restricted. It is also less efficient on fats and sugars (which have a smaller molecular dipole moment) than on liquid water.[10] Microwave heating is sometimes explained as a resonance of water molecules, but this is incorrect: such resonance only occurs in water vapor at much higher frequencies, at about 20 GHz.[11] Moreover, large industrial/commercial microwave ovens operating at the common large industrial-oven microwave heating frequency of 915 MHz—wavelength 328 millimetres (12.9 in)—also heat water and food perfectly well.[12] |
3樓2012-11-04 12:22:48
郭德綱
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4樓2012-11-05 18:06:38
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