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[求助]
物理学大师：微波炉的利与弊？
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多年前俺看到某人在某篇文章，现在在微博上中说“微波是通过电场变化让食品中的水分子高速旋转、相互摩擦产生热量来加热食品的” 我当时给某人发过email指出过，摩擦是宏观现象，分子这样的微观粒子，没有一个“表面”可以让他们“相互摩擦”，热也是宏观想象，一个分子是没有办法产生出来“热量”或者变热的。但是某人非常坚定的认为是我物理不到家，分子是可以摩擦的，并给我一些国外的网页论证说分子必须要摩擦，微波炉才能加热。 他说除非我找到一个外国的物理学家告诉他说他是错的他才信，这个对我的人际关系挑战过于巨大，所以我也就放弃了说服他。 事隔多年，铁锤飞去又飞来，都快忘了这个事了，今天在果壳网上看到那个路由器辐射的帖子，又想起来这桩往事。到底现在关于微波炉加热原理的的科学权威的解释是啥？ 发帖子前还去看了一眼百度百科的微波炉词条，说得和我的理解差不多，但是也很不严谨，说什么“产生了类似摩擦的现象，使水温升高“，这样的解释显然是满足不了我也说服不了某人的。 微波炉到底是怎么工作的？有何利弊？ 现在微博上炒作很厉害，又说起微波炉容易引起癌症云云。无人能解。 |
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heyang_lu
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【答案】应助回帖
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华丽的飘过: 金币+3, 3q 2012-11-04 13:17:00
华丽的飘过: 金币+3, 3q 2012-11-04 13:17:00
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来自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楼2012-11-04 12:22:48
heyang_lu
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2楼2012-11-04 12:19:53
4楼2012-11-05 18:06:38
heyang_lu
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5楼2012-11-05 22:15:20
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