香港物理學會: 台灣師範大學物理系黃坤福教授 物理園 > 物理新知 物理園 > 物理前沿 物理園 > 攀登物理

Slides:



Advertisements
Similar presentations
Lesson 78 Pre-read Answer the following questions. 1.Do you keep a diary ? What language do you use to write your diary ? 2. What must you write when.
Advertisements

新目标初中英语 七年级下册. Unit 8 I’d like some noodles. Section B Period Two.
allow v. wrong adj. What’s wrong? midnight n. look through guess v. deal n. big deal work out 允许;准许 有毛病;错误的 哪儿不舒服? 午夜;子夜 快速查看;浏览 猜测;估计 协议;交易 重要的事.
Unit 33 The New restaurant. Session I You have chosen everything now, haven’t you? 反意疑问句 I’ve got to order new chairs… order vt. 命令, 定购, 定制 你最好还是去预定一辆出租汽车。
高考短文改错专题 张柱平. 高考短文改错专题 一. 对短文改错的要求 高考短文改错的目的在于测试考生判断发现, 纠正语篇中 语言使用错误的能力, 以及考察考生在语篇中综合运用英 语知识的能力. 二. 高考短文改错的命题特点 高考短文改错题的形式有说明文. 短文故事. 书信等, 具有很 强的实用性.
高考英语阅读分析 —— 七选五. 题型解读: 试题模式: 给出一篇缺少 5 个句子的文章, 对应有七个选项,要求同学们根据文章结构、 内容,选出正确的句子,填入相应的空白处。 考查重点: 主要考查考生对文章的整体内容 和结构以及上下文逻辑意义的理解和掌握。 (考试说明) 选项特点: 主旨概括句(文章整体内容)
桂林市 2011 年高三第二次调研考 试质量分析暨备考教学建议 桂林市教育科学研究所 李陆桂. 二调平均分与一调、 2010 广西高考英语平均分的比较 科目 类别 英语 文科文科 2010 年广西 一调 二调 与 10 年广西相差
期末考试作文讲解 % 的同学赞成住校 30% 的学生反对住校 1. 有利于培养我们良好的学 习和生活习惯; 1. 学生住校不利于了解外 界信息; 2 可与老师及同学充分交流有 利于共同进步。 2. 和家人交流少。 在寄宿制高中,大部分学生住校,但仍有一部分学生选 择走读。你校就就此开展了一次问卷调查,主题为.
智慧老伯的一席話 原稿 : 溫 Sir 中譯 : 老柳 A man of 92 years, short, very well- presented, who takes great care in his appearance, is moving into an old people’s.
短文改错解题技巧 1 )错词 2 )多词 3 )缺词 更正 删除 补漏 短文改错(共 10 小题,每小题 1 分,满分 10 分) 假定英语课上老师要求同桌之间交换修改作文,请你 修改你同桌写的以下作文。文中共有 10 处语言错误, 每句中最多有两处。错误涉及一个单词的增加、删除 或修改。 增加:在缺词处加一个漏字符号(
SanazM Compiled By: SanazM Here Are Some Tips That May Bring You A Beautiful Life! Music: 美麗人生 Angel ( 主題曲 ) Revised By: Henry 以下是一些能帶給你一個美麗人生的秘訣 中文註解:
中考英语补全对话、 书面表达命题与备考 宝鸡市教育局教研室 任军利
Unit 1 Talking about the past(19)
Unit 9 Have you ever been to an amusement park? Section A.
专题八 书面表达.
高中英文第一冊 第七單元 重補修用.
完形填空技巧 CET4.
摘要的开头: The passage mainly tells us sth.
Writing 促销英文信 促销的目的就是要卖出产品,那么怎样才能把促销信写得吸引人、让人一看就对产品感兴趣呢?下面就教你促销信的四步写法。
Unit 11 I like the Spring Festival best
The keys to Unit 2 Section A 趣味英语
Festivals around the world
Unit 7 Protect the Earth (Story time) 觅渡教育集团 王 珏 标题 课时 教师姓名 日期 1.
Key sentences in SC 1. 发明有多种产生方式。 2. 大多数时候,发明的产生源于有人努力地想解决一个难题。
专题讲座 武强中学外语组 制作:刘瑞红.
WRITNG Welcome to enjoy English..
Could you please clean your room?
Unit 4 I used to be afraid of the dark.
Life relies on sports 生命在于运动.
Been During the Vacation?
Unit 2 What should I do?.
Teaching aims 1.To remember and master the usage of the key words and phrases. (记住并掌握重要单词及短语的用法) 2.To translate the sentences in the text freely. ( 能熟练的翻译课文)
Here Are Some Tips That May Bring You A Beautiful Life!
B1-05 Free Hugs for All 第5課 對所有人免費擁抱
如何製作 「保家舒」 堆肥 ,………………. 1 1.
Unit 5 Why do you like pandas?
DESERT.
BII.U.VI 一、.Words I. shame n 1. 羞耻(心),羞愧(感)U 2. 羞辱,耻辱
The Wise Old Man 智慧老伯的一席話 原稿: 溫Sir 中譯 : 老柳 中譯潤稿:風刀雨箭
塑膠材料的種類 塑膠在模具內的流動模式 流動性質的影響 溫度性質的影響
A Burning Heart Luke 24: 13 – 35 路加 二四:
中国农村沼气政策与发展战略 李景明 中国北京 农业部科技发展中心能源生态处处长 中国沼气学会秘书长.
Could you please clean your room?
英语教学课件 九年级全.
Reading   这是中等职业学校英语3(高等教育出版社)第一单元Reading的课件。课文内容是:Mr. Hall为了搞一个别具一格的圣诞聚会,在结了冰的河面上搬上了自己起居室的家具和地毯,过了一个快乐的聚会。结果,他喝高了,第二天醒来的时候,河面冰雪融化,家具和地毯都随着河水流向了大海。
Here Are Some Tips That May Bring You A Beautiful Life!
Here Are Some Tips That May Bring You A Beautiful Life!
Here Are Some Tips That May Bring You A Beautiful Life!
Unit 8 Our Clothes Topic1 What a nice coat! Section D 赤峰市翁牛特旗梧桐花中学 赵亚平.
汉英翻译对比练习.
BORROWING SUBTRACTION WITHIN 20
The Wise Old Man 智慧老伯的一席話 原稿: 溫Sir 中譯 : 老柳
关联词 Writing.
高考英语 单项选择题语境探微 长沙市周南中学 杨捷.
精品学习网---初中频道 海量同步课件、同步备考、同步试题等资源免费下载!
成才之路 · 英语 人教版 · 必修1 路漫漫其修远兮 吾将上下而求索.
中考英语阅读理解 完成句子命题与备考 宝鸡市教育局教研室 任军利
浅谈高中英语阅读教学中的问题设计 浙江省临安中学 方利春.
Advance with English 牛津高中英语 (模块七 ·高二下学期).
Philosophy of Life.
高考应试作文写作训练 5. 正反观点对比.
____________________________________
定语从句 ●关系词的意义及作用 : 定语从句一般都紧跟在它所修饰名词后面,所以如果在名词或代词后面出现一个从句,根据它与前面名词或代词的逻辑关系来判断是否是定语从句。
M; Well, let me check again with Jane
英语单项解题思路.
语法填空.
The Wise Old Man 智慧老伯的一席話 原稿: 溫Sir 中譯 : 老柳
高考英语短文改错答题技巧 砀山中学 黄东亚.
高考英语作文指导 福建省教研室 姚瑞兰.
Train Track and Children
Presentation transcript:

香港物理學會: 台灣師範大學物理系黃坤福教授 物理園 > 物理新知 物理園 > 物理前沿 物理園 > 攀登物理 http://www.hk-phy.org/articles/index.html#daily 台灣師範大學物理系黃坤福教授 物理園 > 物理新知 物理園 > 物理前沿 物理園 > 攀登物理

日常生活中常遇到的幾個有趣物理 超聲波的應用: 立體超聲波成像技術可清晰地顯示胎兒的樣貌和細致的動態。 用雷達偵測車速: 立體超聲波成像技術可清晰地顯示胎兒的樣貌和細致的動態。    用雷達偵測車速: 運用多普勒效應,請超速駕駛者「吃牛肉乾」!    單面反光鏡!: 單面反光鏡是否真的可以讓光從其中的一面通過,而在另一面就被反射回去呢?   拯救被磁化了的電視機!: 拯救被頑皮小孩「弄壞了」的電視機!   

幾個有趣的生活物理主題 有趣的拍: 以一個有趣的力學例子,為你說明拍的原理。 過山車的物理: 以一個有趣的力學例子,為你說明拍的原理。    過山車的物理: 為甚麼過山車不需要引擎來推動?為甚麼我們倒轉了卻不會掉下來?    「跳樓機」的物理: 為甚麼在遊樂場的「跳樓機」中下墜會感受到「無重狀態」?這和太空人感受到的「無重狀態」有甚麼相似的地方?  如何踢出「香蕉波」? 射手如何踢出一個帶有旋轉的球,巧妙地繞過人牆?  

幾個有趣的生活物理主題 鞦韆的聯想 把鞦韆盪得越來越高,在物理學上是一種共振現象! CD-ROM 的工作原理 神奇的「鐳射避雷針」 避雷針的原理是什麼?鐳射與避雷針又有甚麼關係呢?    微波爐的原理 用微波爐煮食有甚麼好處?為甚麼它可以很快把食物加熱?   

幾個有趣的生活物理主題 電冰箱的原理 你有沒有想過電冰箱的結構呢? 揚聲器的原理 揚聲器應用了電磁鐵來把電流轉化為聲音。 神奇暖袋的原理 你有沒有想過電冰箱的結構呢?    揚聲器的原理 揚聲器應用了電磁鐵來把電流轉化為聲音。    神奇暖袋的原理 這種暖袋不用電力,也不用熱水,實在是神奇哩!

微 波 爐 雜 談 http://tj.xinhuanet.com (2003/11/20紀錄)

The microwave oven is one of the great inventions of the 20th century http://home.howstuffworks.com/microwave3.htm The microwave oven is one of the great inventions of the 20th century - millions of homes in America have one. Just think about how many times you use a microwave every day - and not only at home. You're running late for work, so there's no time to fix breakfast at home. On your way to the office, you stop to gas up your car. Inside the quickie-mart, you grab a frozen breakfast burrito and pop it in the microwave on the counter. Later that day, you have to work through lunch. By 3:00 p.m., you're starving, so you grab a snack-pack of microwaveable popcorn from the vending machine and pop that in the break-room microwave. That night, after a really long day at work, you're simply too tired to grill out, so you dish up last night's lasagna and heat it up in the microwave...

Why are microwave ovens popular? Because they cook food in an amazingly short amount of time. They are also extremely efficient in their use of electricity because a microwave oven heats only the food - nothing else. In this article, we'll discuss the mystery behind the magic of "meals in a minute" with microwave cooking.

Cooking in conventional oven To bake a cake in a conventional oven. Normally you would bake a cake at 350 degrees F or so, but let's say you accidentally set the oven at 600 degrees instead of 350. What is going to happen is that the outside of the cake will burn before the inside even gets warm. In a conventional oven, the heat has to migrate (by conduction) from the outside of the food toward the middle (See the HSW article entitled How a Thermos Works for a good explanation of conduction and other heat transfer processes). You also have dry, hot air on the outside of the food evaporating moisture. So the outside can be crispy and brown (e.g. - bread forms a crust) while the inside is moist.

Ready, Set, Cook!

Microwave Cooking The radio waves penetrate the food and excite water and fat molecules pretty much evenly throughout the food. There is no "heat having to migrate toward the interior by conduction". There is heat everywhere all at once because the molecules are all excited together. There are limits of course: Radio waves penetrate unevenly in thick pieces of food they don't make it all the way to the middle, and there are also "hot spots" caused by wave interference, but you get the idea. The whole heating process is different because you are "exciting atoms" rather than "conducting heat".

Microwave cooking In a microwave oven, the air in the oven is at room temperature. So there is no way to form a crust. That is why foods like "Hot Pockets" come with a little cardboard/foil sleeve. Put the food in the sleeve and then microwave it. The sleeve reacts to microwave energy by becoming very hot. This exterior heat lets the crust become crispy as it would in a conventional oven.

How Does A Microwave Oven Work? Basic Theory of Operation http://home.howstuffworks.com/framed.htm?parent=microwave.htm&url=http://www.gallawa.com/microtech/how_work.html

On the Radio A microwave oven uses microwaves to heat food. Microwaves are radio waves. In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,450 megahertz (2.45 GHz). Radio waves in this frequency range have an interesting property: They are absorbed by water, fats and sugars. When they are absorbed they are converted directly into atomic motion -- heat. Microwaves in this frequency range have another interesting property: they are not absorbed by most plastics, glass or ceramics. Metal reflects microwaves, which is why metal pans do not work well in a microwave oven.

微波爐的起源 1946年,美國雷聲公司研究員斯潘瑟(Dr. Percy Spencer, a self-taught engineer with the Raytheon Corporation) 在一個偶然的機會,發現微波會將糖果溶化。 實驗證明,微波輻射確實能引起食物內部水分子的振動,從而產生熱量。 1947年,第一台微波爐問世。 Dr. P. Spencer 世界第一台微波爐

"Who Invented Microwaves?" Asking this problem likes asking who invented electricity. Microwave energy is a natural phenomenon that occurs when electric current flows through a conductor. Microwaves are a form of electromagnetic radiation that is very similar to sunlight and radio waves.

Discovery of Microwave Oven It was discovered around 1946 during a radar-related research project. Dr. Percy Spencer, a self-taught engineer with the Raytheon Corporation, noticed something very unusual. He was testing a new vacuum tube called a magnetron (we are searching for a picture of an actual 1946 magnetron). He discovered that the candy bar in his pocket had melted. This intrigued Dr. Spencer, so he tried another experiment. This time he placed some popcorn kernels near the tube and, perhaps standing a little farther away, he watched with an inventive sparkle in his eye as the popcorn sputtered, cracked and popped all over his lab.

Heating Effect of Microwave on an Egg The next morning, Scientist Spencer decided to put the magnetron tube near an egg. Spencer was joined by a curious colleague. They both watched as the egg began to tremor and quake. The rapid temperature rise within the egg was causing tremendous internal pressure. Evidently the curious colleague moved in for a closer look just as the egg exploded and splattered hot yolk all over his amazed face.

Heating Effect of Microwave on an Egg The face of Spencer lit up with a logical scientific conclusion: The melted candy bar, the popcorn, and now the exploding egg, were all attributable to exposure to low-density microwave energy. Thus, if an egg can be cooked that quickly, why not other foods? Experimentation began...

First Microwave Oven Dr. Spencer fashioned a metal box with an opening into which he fed microwave power. The energy entering the box was unable to escape, thereby creating a higher density electromagnetic field. When food was placed in the box and microwave energy fed in, the temperature of the food rose very rapidly. Dr. Spencer had invented what was to revolutionize cooking, and form the basis of a multimillion dollar industry, the microwave oven.

First Microwave Oven -Nearly 6 Feet Tall, weighing 750 Pounds Engineers went to work on Spencer's hot new idea, developing and refining it for practical use. By late 1946, the Raytheon Company had filed a patent proposing that microwaves be used to cook food.

Origin Microwave Oven Patent

The world’s first microwave oven An oven that heated food using microwave energy was then placed in a Boston restaurant for testing. At last, in 1947, the first commercial microwave oven hit the market. These primitive units where gigantic and enormously expensive, standing 5.5 feet tall, weighing over 750 pounds, and costing about $5000 each. The magnetron tube had to be water-cooled, so plumbing installations were also required.

Initial Reactions Were Unfavorable Not surprisingly, many were highly reluctant about these first units, and so they found only limited acceptance. Initial sales were disappointing...but not for long. Further improvements and refinements soon produced a more reliable and lightweight oven that was not only less expensive, but, with the development of a new air-cooled magnetron, there was no longer any need for a plumber.

To use in food industry The microwave oven had reached a new level of acceptance, particularly with regard to certain industrial applications. By having a microwave oven available, restaurants and vending companies could now keep products refrigerator-fresh up to the point of service, then heat to order. The result? Fresher food, less waste, and money saved.

New and Unusual Applications As the food industry began to recognize the potential and versatility of the microwave oven, its usefulness was put to new tests. Industries began using microwaves to dry potato chips and roast coffee beans and peanuts. Meats could be defrosted, precooked and tempered. Even the shucking of oysters was made easier by microwaves.

Applications in other industries Other industries found the diverse applications of microwave heating quite advantageous. In time, microwaves were being used to as a dry meachine. To dry cork, ceramics, paper, leather, tobacco, textiles, pencils, flowers, wet books and match heads. The microwave oven had become a necessity in the commercial market and the possibilities seemed endless.

The First "Radar Range" In 1947, Raytheon demonstrated the world's first microwave oven called it a "Radarange," the winning name in an employee contest. The first ovens housed in refrigerator-sized cabinets, cost between $2,000 and $3,000. Sometime between 1952-55, Tappan introduced the first home model priced at $1295. In 1965 Raytheon acquired Amana Refrigeration. Two years later (1967), the first countertop, domestic oven was introduced. It was a 100-volt microwave oven, which cost just under $500 and was smaller, safer and more reliable than previous models.

By 1975 Sales of Microwave Ovens Exceeded that of Gas Ranges Technological advances and further developments led to a microwave oven that was polished and priced for the consumer kitchen. However, there were many myths and fears surrounding these mysterious new electronic "radar ranges." By the seventies, more and more people were finding the benefits of microwave cooking to outweigh the possible risks, and none of them were dying of radiation poisoning, going blind, sterile, or becoming impotent (at least not from using microwave ovens). As fears faded, a swelling wave of acceptance began filtering into the kitchens of America and other countries. Myths were melting away, and doubt was turning into demand.

Fast growth rate By 1975, sales of microwave ovens would, for the first time, exceed that of gas ranges. The following year, a reported 17% of all homes in Japan were doing their cooking by microwaves, compared with 4% of the homes in the United States the same year. Before long, though, microwave ovens were adorning the kitchens in over nine million homes, or about 14%, of all the homes in the United States. In 1976, the microwave oven became a more commonly owned kitchen appliance than the dishwasher, reaching nearly 60%, or about 52 million U.S. households. America's cooking habits were being drastically changed by the time and energy-saving convenience of the microwave oven. Once considered a luxury, the microwave oven had developed into a practical necessity for a fast-paced world.

An Expanding Market An expanding market has produced a style to suit every taste; a size, shape, and color to fit any kitchen, and a price to please almost every pocketbook. Options and features, such as the addition of convection heat, probe and sensor cooking, meet the needs of virtually every cooking, heating or drying application. Today, the magic of microwave cooking has radiated around the globe, becoming an international phenomenon.

Inventor Dr. Percy Spencer Doctor Spencer continued at Raytheon as a senior consultant until he died at the age of 76. At the time of his death, Dr. Spencer held 150 patents and was considered one of the world's leading experts in the field of microwave energy, despite his lack of a high school education.

On September 18, 1999, Dr. Percy LaBaron Spencer was inducted into the National Inventors Hall of Fame and took his place in history alongside such great inventors as Thomas Edison, the Wright Brothers and George Washington Carver. More to come on the fascinating history and development of the microwave oven... Note: Photo of Percy Spencer and Patent provided courtesy of The Spencer Family Archives Picture of the earliest microwave oven provided courtesy of The Lemelson-MIT Awards Program's Invention Dimension web site, http://web.mit.edu/invent

More Information More about the myths & mysteries of microwave ovens http://www.gallawa.com/microtech/index.html Microwave Oven Operation, Troubleshooting and Repair Advice for Appliance and Electronic Technicians.

傳統煮食方法是用火加熱,通過鍋底傳熱給鍋中的食物,食物受熱是從表面逐漸傳遞到裡面的。這種方法有兩個缺點: 調理食物所花費的時間長, 會破壞食物中的維生素、天然風味 和色澤。 大塊的食物不能內外同時煮熟, 常造成內生外焦的現象。 微波爐的加熱方式可克服上述兩缺點。 具有清潔、快速、方便等諸多優點

微波是一種高頻率、短波長的電磁波 頻率在300MHz-3000GHz,波長範圍在1mm -1 m 間的電磁波。 家用微波爐的微波功率,一般從 0.6 kW 到 2 kW之間。 國際規定家用微波爐所使用之微波的頻率為 2.45 GHz,此頻率避開了通訊電波的頻段,以避免干擾現在大量使用的通訊系統。 其在空氣中的波長為 12.2cm, 但在食物中的波長低於12 cm 電磁波在不同材料中傳遞時,其每單位時間內的震盪頻率不會改變,但電磁波的傳播速度v和波長會隨材料的導電係數r和導磁係數r不同而改變, 關係是如下右:

微波爐加熱的工作原理 無火煮食:都市飲食的潮流 微波是一種高頻率、短波長的無線電波,與一般電視和收音機接收到的電磁波和紫外光燈發射的紫外光波相近。 微波本身並不生熱, 水分子和食物同時摩擦生熱:然而當微波使食物中的水、油脂、糖及蛋白質等極性分子互相摩擦的時候,便會產生熱量--; 如同我們快速地摩擦自己雙手的時候,也會發熱一樣。 微波使食物中的極性分子在一種令人難以置信的高速頻率下振動(約為2.45 GHz),這種驚人的速度使食物中的分子自行產生熱量來煮熟食物。 微波爐正是利用這一原理來進行食物的烹飪

為甚麼微波能快速加熱食品呢? 微波可以很容易地穿透絕緣物體, 但遇到有水份的食物便會使水分子和它一起以相同的頻率振盪,振盪中分子與分子互相摩擦,因而產生熱量。 水分子在微波中每秒振盪 2.45 GHz,這種微波振盪幾乎是在食物的內外各部分同時發生, 故微波加熱的食品能夠在很短的時間內,把整份食物煮熟。 因此微波爐烹飪,熱量是直接深入食物內部 所以,烹飪速度比其他爐灶快4至10倍,熱效率高達80%以上。目前,其他各種爐灶的熱效率無法與它相比。 目前在美國的使用率高達 90%。

微波爐的四大好處 經濟省時: 比傳統的烹調方法最低限度節省一半時間。微波電子爐的加熱時間快速,翻煮的食物可以保持原狀, 在處理的過程中,也不需翻動食物,因此不但可以保持食物的原樣,並且也節省了煮熟食物然後排碟上菜的時間。 所以利用微波電子爐來烹調食物,的確能為 我們節省許多時間,實在合乎經濟之道。

微波爐的好處 容易保持地方清潔: 微波煮食是基於微波和食物中的水分子異性相吸的緣故,產生高速的振動。 不需任何傳熱的媒介,也不必利用對流或傳導等傳統加熱。 因此,室內的空氣不會熱,溫度也不會提高。 廚房內的桌面和牆壁等都很容易保持清潔,清洗的工作也簡單得多。 在烹煮食物時,也不會因熱氣而汗流夾背。

微波爐的好處 能保存食物營養,顏色以及原味: 微波煮食的速度很快,故能較好地保存一些對熱敏感和水溶性的維生素,如維生素B和C。 醃肉、臘肉、鹹魚和熏鴨等食品在加工過程中會產生亞硝胺。 但是,經研究發現,將醃肉放在微波爐內烤45分鐘後取出來,不但口味沒有改變, 而且更加香濃,更重要的是經過化學分析,裏面並沒有亞硝胺這種成分。 當微波爐烹任食品時,因為加熱的能量直接達到食品內部,所以加熱均勻,無需翻炒,不會產生外焦內生的現象。 因此,微波煮食是健康的煮食方法。

微波爐的好處 解凍迅速: 可一次購買較大量的食物,存放在冰箱內, 或預先把菜肴預備好,急凍存放在冰箱內。 需用時才利用微波爐解凍、烹調或翻熱。 既方便,亦節省了購買食物的時間。

微波爐使用訣竅 鋁箔紙的使用:雞翅尖、雞胸或魚頭、魚尾部或蛋糕的角端等部位易於烹調過度,用鋁箔紙遮裹可達到烹調均勻目的。 器皿蓋或保鮮膜封蓋的使用:蒸煮、燉食物和炒蔬菜時,為保持食物原汁、原味,防止水分過多蒸發,加快烹飪速度,應使用器皿蓋或保鮮膜。 紙巾、布巾的使用:烘烤麵包、餅乾或粘有麵包屑的雞肉片豬肉片時,用紙巾墊在食物底下,可保持食物表面乾燥、鬆脆。做饅頭、糕餅時可用濕紗布或紙巾封蓋或包卷,可防水分蒸發。

微波爐使用訣竅 攪拌與重置:中途對湯類攪拌,對肉片、 牛排翻轉或對相互重疊較嚴重的食品進行 重置,有助於增強烹飪效果。 擱放與調味:在加熱結束時,把食物擱置 一段時間或對有些食品添配一些佐料(如烹 飪家禽肉類後,可澆上乳化的油或調味汁, 再撒些辣椒粉、麵包屑等),可達到加熱不 能做到的滿意效果。

微波爐的基本外型 導波管 磁控管 冷卻裝置 微波 轉盤

微波爐的基本外型和結構 ②視屏窗:有金屬遮罩層,可透過網孔觀察食物的烹飪情況。 ③通風口:確保烹飪時通風良好; ①門安全聯鎖開關:確保當爐門開啟時,微波爐不會發射微波工作;只有在爐門關上時,微波產生器才會啟動微波工作; ②視屏窗:有金屬遮罩層,可透過網孔觀察食物的烹飪情況。 ③通風口:確保烹飪時通風良好; ④轉盤支承:帶動玻璃轉盤轉動; ⑤玻璃轉盤:放置裝好食物的 容器轉盤,加熱時可轉盤轉 動,以使均勻食物烹飪; ⑥控制板:控制各檔烹飪; ⑦爐門開關,按此開關, 爐門打開。 導波管 磁控管 冷卻裝置 微波 轉盤

微波是否會外洩? 各大生產廠商在設計/製造微波爐時,早就解決此問題。 採用了三級連鎖防護技術,對微波爐內的運轉形成了三層監管措施,以層層監控。 第一層最初級的防洩方式,稱為機械防洩漏: 主要靠爐門的密封性來實現防微波洩漏。 當微波爐接上電源時,爐內的磁控管(Magnetron)便會產生微波 再由一個微波攪動器把微波擴散至爐的各部分。 爐門是用兩層透明玻璃夾著一層金屬網構成的,以使微波不能外泄,且會在爐的四壁向內反射,使微波的分佈更平均。

微波是否會外洩? 此外,國外一些著名微波爐製造商亦多採用了下列兩道相應的防洩措施,使整個微波爐的微波洩漏控制到最小。 利用微波本身的反射特性,採用環繞抑制的結構。 利用先進的連鎖微電腦電控機構可以及時切斷磁控管的工作電源,以確保無微波洩漏: 以防遇到不可預見的原因,微波爐爐門突然打開時所造成的大量洩漏。 對微波洩露形成了三層監管的措施,所以我們大可不必擔憂微波的洩露會威脅到我們的健康以至生命安全!

微波的電磁特性 微波不僅具有電磁波的粒子和波的雙重性質,且因其波段緊鄰可見光波段,所以具有許多和光類似的光學和電磁特性。 如同可見光碰到鏡子會發生反射,微波也具有反射特性,即當微波遇到金屬便反射回來。 所以用金屬容器盛載食物,在微波爐中不能被加熱,長時間還可能損壞微波爐。 原因是微波產生器的磁控管所發射出去的微波會沒有損耗地全部反射回來,後果會使發射微波的產生器產生高溫,以致損壞。 因此用微波爐煮食物,應選用耐熱的絕緣材料製成的容器,如陶瓷、耐熱玻璃或塑膠等。

微波爐洩漏的國際標準 -必須低於 5 mW/cm2 微波爐工作所產生的輻射甚至比一根普通日光燈管還要少。 目前,微波爐洩漏的國際標準是每平方釐米不超過 5毫瓦 (5mW)。 可見,微波爐是一種安全的家電,不會對人的健康產生任何危害,大家使用微波爐時不必誠惶誠恐。

微波加熱法對食物的影響 食物經過微波後﹐並不會產生有害物質﹐也不會殘留放射性物質。 但食物經加熱後,或多或少會造成水溶性維生素之營養素的損失,如維生素B群與C等。 和一般的加熱方法相比,如煮與蒸等,以微波加熱的維生素B群耗損率與一般加熱法相近。 但維生素C耗損率就比一般加熱法低了。 尤其和需要消耗許多時間的烹調方式,如燉煮之調理等比起來,微波加熱所能保存的水溶性維生素量就更多了。

微波爐的工作原理 用微波來煮飯燒菜。 微波是一種電磁波,此頻段的電磁波能量不僅比以往使用的無線電波大得多,且還很有“個性”: 微波一碰到金屬材料會被反射 所以金屬根本沒有辦法吸收或傳導微波; 但可以穿透玻璃、陶瓷、塑膠等絕緣材料,而不會完全消耗能量; 但含有水分的食物,微波不但不能穿透,且其能量反而會被吸收,進而使得水分產生共振現象。

微波爐的結構 外殼使用不銹鋼等金屬材料製成,可以阻擋微波從爐內逃出,以免影響人們的身體健康。 裝食物的容器則用絕緣材料製成。 磁控管(magnetron tube)-微波爐的心臟 磁控管的電子管是微波發生器,能產生每秒鐘振動頻率為 2.45 GHz 的微波。

使用微波爐時需小心的地方 盛裝食物的容器如果是金屬或鍍有金屬容器,會反射微波,讓微波無法射入食物之中,最後無法加熱。 如果容器上有金屬線的,如瓷器上裝飾的金色邊,還會產生火花﹐造成危險。 雞蛋也不可放入微波爐加熱,蛋中的水份會因加熱變成水蒸氣而將蛋炸開,成為炸蛋(彈)。 建議使用專門用於微波加熱的塑膠容器盛裝食物加熱,可避免有害物質的滲出。 使用保鮮膜時,為保險起見,建議避免讓保鮮膜直接接觸食物。 

使用微波爐時需小心的地方 微波爐最受稱道的用途還是熱剩菜: 不但方便,而且可以保留更多的營養素。 但微波加熱的過程,會造成食物中的水份散失,所以吃起來比較乾。 故以微波爐加熱的食物或便當,要趁熱吃為宜。冷了,口感就變差了。 尤其米食等澱粉類的食物﹐吃起來會相當乾硬。

加熱食物的原理 以微波加快食物中所有的水分子同時一起轉動而生熱,使食物加熱。肉眼看不見的微波,能穿透食物達 5 cm 深 並使食物中的水分子也隨之運動, 劇烈的水分子運動會產生大量的熱能, 而將食物“煮”熟。 用普通爐灶煮食物時,熱量總是從食物外部逐漸進入食物 的內部。 而用微波爐烹飪,熱量則是直接深入食物內部, 故烹飪速度比其他爐灶快4-10倍,熱效率高達80%以上。是目前其他各種爐灶的熱效率無法與之相比。

微波爐加熱的原理 微波本身可以加快食物中水分子的轉動,在轉動的過程中摩擦生熱,使食物完成加熱。 食物經過微波後,並不會產生有害物質,也不會殘留放射性物質。 但是食物經加熱後,或多或少會造成水溶性維生素,如維生素B群與C等營養素的損失。 和一般加熱方法相比(如煮與蒸等),微波加熱所產生的維生素B群耗損率與一般加熱法相近,但維生素C耗損率就比一般加熱法低了。 尤其和需要消耗許多時間的烹調方式,如燉等,比起來﹐微波加熱所能保存的水溶性維生素量就更多了。

微波爐烹飪食物的優點 微波爐烹飪所需的時間很短,故能較有效率地保持食物中的維生素和天然風味。 以微波加熱維生素 B 群所產生的耗損率與一般加熱法相近,但對維生素C的耗損率就比一般加熱法低許多。 如用微波爐煮青豌豆,幾乎可以使維生素C一點都不損失。 此外,微波還可以消毒殺菌。

其實微波爐最受稱道的用途還是熱剩菜,不但方便,而且可以保留更多的營養素。 不過﹐微波加熱的過程,會造成食物中的水份散失,所以吃起來比較乾。 以微波爐加熱的食物或便當,要趁熱吃為宜。冷了﹐口感就變差了。尤其米食等澱粉類的食物﹐吃起來會相當乾硬。

微波也是電磁波的一種﹐通常微波爐有良好的防護設計,以阻隔電磁波的外洩。 即使電器的阻隔不良﹐造成少量的微波外洩,只要不是離爐太近﹐對健康是沒什麼妨害的。 本文的重點則放在微波爐加熱對於食物營養的影響﹐以及使用微波爐的所應注意的事項上。 

使用微波爐時需小心的事項 盛裝食物的容器如果是金屬或鍍有金屬容器,會反射微波,讓微波無法射入食物之中,最後無法加熱。 如果容器上有金屬線的,如瓷器上裝飾的金色邊,則易產生火花,造成危險(李安導演的代表作『推手』有這樣的一個情節)。 雞蛋也不可放入微波爐加熱,蛋中的水份會因加熱變成水蒸氣而將蛋炸開,成為炸蛋(彈)。 建議使用專門用於微波加熱的塑膠容器盛裝食物加熱,可避免有害物質的滲出。 使用保鮮膜時,為保險起見,建議避免讓保鮮膜直接接觸食物。 

使用微波爐應注意的事項 不可使用金屬容器 任何內含大量水分,但表面密封好的食物或容器,不能使用微波爐加熱,否則亦產生爆炸現象。 如密封的蛋殼、和含有整顆蛋黃的雞蛋,因蛋黃表面有一層密封的膜層也不能使用微波加熱。 使用微波爐時,應注意不可以空“燒”。 因空“燒”時,微波的能量無法被任何物質吸收,如此很容易損壞磁控管。 另外,因人體組織中含有高達 70% 的大量水分,故若在微波爐產生微波能量時打開爐門,則會很容易吸收微波爐所產生的能量。 一定要在磁控管停止工作後,再打開爐門,提取食物。

微波爐的基本外型 導波管 磁控管 冷卻裝置 微波 轉盤

微波爐的基本外型和結構 ②視屏窗:有金屬遮罩層,可透過網孔觀察食物的烹飪情況。 ③通風口:確保烹飪時通風良好; ①門安全聯鎖開關:確保當爐門開啟時,微波爐不會發射微波工作;只有在爐門關上時,微波產生器才會啟動微波工作; ②視屏窗:有金屬遮罩層,可透過網孔觀察食物的烹飪情況。 ③通風口:確保烹飪時通風良好; ④轉盤支承:帶動玻璃轉盤轉動; ⑤玻璃轉盤:放置裝好食物的 容器轉盤,加熱時可轉盤轉 動,以使均勻食物烹飪; ⑥控制板:控制各檔烹飪; ⑦爐門開關,按此開關, 爐門打開。 導波管 磁控管 冷卻裝置 微波 轉盤

詳細工作原理

(1) 爐腔 (Oven chamber) 爐腔是一個微波諧振腔(Resonating cavity),此為將微波能轉變為熱能,對食品進行加熱的空間。 為使爐腔內的食物均勻受熱,爐腔內設有特別的裝置: 早期的微波爐在爐腔頂部裝有金屬扇頁,作為微波攪拌器,以干擾微波在爐腔中的均勻傳播,以使食物加熱較為均勻。 目前則是在微波爐的爐腔底部裝置一個由微型馬達帶動的玻璃轉盤,把擬加熱的食品放在轉盤上與轉盤一起繞電機軸旋轉,使其與爐內的高頻電磁場作相對運動,來達到爐內食品均勻加熱的目的。 大陸產商則另獨創自動升降型的轉盤,期使加熱更均勻,烹飪效果更理想。

(2) 爐 門 - 1 食品的進出口,也是爐腔的重要組成部分: 此裝置的規格要求很高,要能從門外可以觀察到爐腔內食品加熱的情況,又並需防止微波不能洩漏出來。 爐門由金屬框架和玻璃觀察窗組成。 觀察窗的玻璃夾層中有一層金屬微孔網,既可透過它看到食品,又可防止微波外洩。 金屬網的網孔(網目)大小是經過精密計算,至少必須比微波在玻璃中傳遞時之波長的1/4倍小,如此即可完全阻擋微波穿透玻璃爐門。

(2) 爐 門 - 2 為了防止微波的洩漏,微波爐的開關系統也採用多重安全聯鎖微動開關裝置。 爐門若沒有關好,就不能啟動微波產生器,產生微波,也不會進行加熱工作。微波爐不工作,就談不上有微波洩漏的問題了。

(2) 爐 門 - 3 為防止微波從爐門與腔體間的縫隙中洩漏出來 早期使用能吸收微波的材料做門封條,如用矽橡膠門封條,以將可能洩漏的少量微波吸收掉。 但因門封條容易破損或老化,大幅降低防洩作用。 現在則大多採用在爐門四周設計抗流槽結構,防 止微波外洩。 即在門內設置一條異型槽結構,使其具有引導微波反轉相位的作用。

抗流槽結構 防微波輻射外洩的原理 抗流槽結構是從微波輻射的原理上得到的防止微波洩漏的穩定可靠的方法。 發射的微波在抗流槽入口處,會被此結構反轉相位,成為逆向的反射波,進而和入射波相互抵銷,如此微波就不會外洩了。 廣東格蘭仕企業公司生產的格蘭仕微波爐所採用的就是抗流槽防洩結構,加上其開發研製的多重防微波洩漏技術,使微波洩漏控制技術達到國際先進的水準。

(3)電子(電器)電路 主要含有三部分 高壓電路 控制電路 低壓電路

(3a) 高壓電路 高壓電路為電源高壓變壓之次級線圈繞組之後的電路,主要包括 磁控管 高壓電容器 高壓變壓器 高壓二極體

磁控管/高壓電路部分 磁控管是微波爐的心臟,微波能就是由此產生並發射出來的,故又稱微波產生器。 磁控管需要很高的直流陽極電壓(>600 V)和約3~4V的陰極電壓,才能運作製造微波。 由高壓變壓器及高壓電容器、高壓二極體構成的倍壓整流電路即提供了磁控管所需的工作電壓。

Configuration Microwave ovens use various combinations of electrical circuits and mechanical devices To produce and control an output of microwave energy for heating and cooking. The systems of a microwave oven can be divided into two fundamental sections,   Control section & High-voltage section 

Control & High Voltage Sections The control section consists of A timer (electronic or electromechanical), A system to control or govern the power output, Various interlock and Protection devices. The high voltage is then converted microwave energy.

How it works? Basically, electricity from the wall outlet travels through the power cord and enters the microwave oven through a series of fuse and safety protection circuits. These circuits include various fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an overheating condition occurs. If all systems are normal, the electricity passes through to the interlock and timer circuits. When then oven door is closed, an electrical path is also established through a series of safety interlock switches . Setting the oven timer and starting a cook operation extends this voltage path to the control circuits .

How Microwave forms? Basically, electricity from the wall outlet travels through the power cord, then enters the microwave oven through a series of fuse and safety protection circuits. These circuits include various fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an overheating condition occurs. If all systems are normal, the electricity passes through to the interlock and timer circuits. When then oven door is closed, an electrical path is also established through a series of safety interlock switches . Setting the oven timer and starting a cook operation extends this voltage path to the control circuits .

How control system works? Generally, the control system includes either an electromechanical relay or an electronic switch called a triac as shown in Figure 2 . Sensing that all systems are "go," the control circuit generates a signal that causes the relay or triac to activate, thereby producing a voltage path to the high-voltage transformer. By adjusting the on-off ratio of this activation signal, the control system can govern the application of voltage to the high-voltage transformer, thereby controlling the on-off ratio of the magnetron tube and therefore the output power of the microwave oven. Some models use a fast-acting power-control relay in the high-voltage circuit to control the output power.

How control system works? Generally, the control system includes either an electro-mechanical relay or an electronic switch called a triac. Sensing that all systems are "go," the control circuit generates a signal that causes the relay or triac to activate, thereby producing a voltage path to the high-voltage transformer. By adjusting the on-off ratio of this activation signal, the control system can govern the application of voltage to the high-voltage transformer, thereby controlling the on-off ratio of the magnetron tube and therefore the output power of the microwave oven. Some models use a fast-acting power-control relay in the high-voltage circuit to control the output power.

High-voltage Section The high-voltage transformer along with a special diode and capacitor arrangement serve to increase the typical household voltage (110-115 V), to the shockingly high amount of ~3 kV! While this powerful voltage would be quite unhealthy -- even deadly -- for humans, it is just what the magnetron tube needs to do its job - that is, to dynamically convert the high voltage in to undulating waves of electromagnetic cooking energy.

Electric Path of Microwave

High-voltage Section Waveguides: The microwave energy is transmitted into the metal channel, which feeds the energy into the cooking area It also encounters the slowly revolving metal blades of the stirrer blade. Some models use a type of rotating antenna while others rotate the food through the waves of energy on a revolving carousel. In any case, the effect is to evenly disperse the microwave energy throughout all areas of the cooking compartment. Some waves go directly toward the food, others bounce off the metal walls and flooring; and, thanks to special metal screen, microwaves also reflect off the door. So, the microwave energy reaches all surfaces of the food from every direction.

High-voltage Section The microwave energy reaches all surfaces of the food from every direction. All microwave energy remains inside the cooking cavity. When the door is opened, or the timer reaches zero, the microwave energy stops— just as turning off a light switch stops the glow of the lamp. 

低壓電路&控制電路 保險絲裝置 熱斷路器保護開關 照明燈 聯鎖微動開關 計時器 功率分配器開關 轉盤電機 、、等等。 風扇電機 高壓變壓器初級繞組之前至微波爐電源入口之間的電路則包括了此兩部分電路,主要包括 保險絲裝置 照明燈 計時器 轉盤電機 風扇電機 熱斷路器保護開關 聯鎖微動開關 功率分配器開關 、、等等。

(4)計時器 基本功能是選擇設定微波工作時間,設定 時間過後,計時器自動切斷微波爐的主電 路電源。 一般有機械式定時和電腦定時兩種計時方 式。

(5)功率分配器 功率分配器用來調節磁控管的平均工作時間 即調節磁控管斷/續工作時間的比例,亦即“工作”和“停止”時間的比例。 從而達到調節微波爐平均輸出功率的目的。 機械控制式一般有3~6個刻度調整檔位,而 電腦控制式微波爐可有10個調整檔位,用以 設定此平均輸出功率。

機械式定時 一般有3~6個刻度調整檔位 定時器(Timer) 電腦定時式 通常有10個調整檔位 或直接設定時間

(6)聯鎖微動開關 聯鎖微動開關是微波爐中一組非常重要的安 全防護裝置。 具有多重聯鎖作用,均通過爐門的開門按鍵 或爐門把手上的開門按鍵加以控制。 當爐門未關閉好或爐門打開時,自動切斷微 波產生器(磁控管)的電源電路,使微波停止 發射。

(7) 熱斷路器 熱斷路器是用來監控磁控管或爐腔工作 溫度的元件。 當工作溫度超過某一限值時,熱斷路器 會立即切斷電源,使微波爐停止工作, 以免燒壞微波爐。

使用、維護上的禁忌 微波爐要放置在通風的地方,附近不要有磁性物質,以免干擾爐腔內磁場的均勻狀態,使工作效率下降。 還要和電視機、收音機、手機等含微波電路的電器離開一定的距離,否則會影響這些電器的視、聽效果。 爐內未放烹飪食品時,不要通電工作。不可使微波爐空載運行,否則會損壞磁控管,為防止一時疏忽而造成空載運行,可在爐腔內置一盛水的玻璃杯。 凡金屬的餐具,竹器、塑膠、漆器等不耐熱的容器,有凹凸狀的玻璃製品,均不宜在微波爐中使用。瓷製碗碟不能鑲有金、銀花邊。 盛裝食品的容器一定要放在微波爐專用 的盤子中,不能直接放在爐腔內。

使用、維護上的禁忌 微波爐的加熱時間要視材料、用量和食物的新鮮程度而定,特別和含水量有關。 按照食物的種類和烹飪要求,調節定時及功率/溫度旋鈕,使用前應仔細閱讀說明書,以瞭解微波爐的特性和注意事項。 由於各種食物加熱時間不一,故在不能肯定食物所需加熱時間時,應以較短時間為宜,加熱後可視食物的生熟程度再追加加熱時間。 否則,如時間太長,會使食物變得 發硬,而失去香、色、味。

使用、維護上的禁忌 帶殼的雞蛋、帶密封包裝的食品不能直接烹調,以免爆炸。 一定要關好爐門,確保連鎖開關和安全開關的閉合。 微波爐關掉後,不宜立即取出食物,因此時爐內尚有餘熱,食物還可繼續烹調,應過1分鐘後再取出。 爐內應經常保持清潔。在斷開電源後,使用濕布與中性洗滌劑擦拭,不要沖洗,勿讓水流入爐內電器中。

使用、維護上的禁忌 不宜把臉貼近微波爐觀察窗,以防止眼睛因微波輻射而受損傷。 也不宜長時間受到微波照射,以防引起頭暈、目眩、乏力、消瘦、脫髮等症狀,使人體受損。 應定期檢查爐門四周和門鎖,如有損壞、閉合不良,應停止使用,以防微波洩漏。

清除微波爐頑垢的妙法 微波爐用過後若不隨即擦拭,很容易在內部結成乾硬難除的油垢,除垢的標準方法如下: 將一個裝有熱水的容器放入微波爐內,加熱 2-3 分鐘,使得微波爐內充滿蒸氣,如此可使頑垢因飽含水分而變得鬆軟,進而容易去除污垢。 清潔時,則可用經稀釋過的中性清潔劑先擦一遍,再分別用清水洗過的乾淨濕抹布和乾淨的乾抹布作最後的清潔。 如果仍不能將頑垢除掉,可以利用塑膠卡片之類的器具來刮除,千萬不能用金屬片刮,以免傷及內部。 最後,別忘了將微波爐門打開,讓內部徹底風乾。

使用微波爐的9個禁忌 忌用普通塑膠容器: 原因一是熱的食物會使塑膠容器變形,二是普通塑膠會放出有毒物質,污染食物,危害人體健康。需使用微波專門的器皿盛裝食物,才能放入微波爐中加熱。 忌用金屬器皿:鐵、鋁、不銹鋼、搪瓷等器皿,在微波爐內加熱時,會與之產生電火花並反射微波,既損傷爐體,又無法加熱不熟食物。 忌使用封閉容器:在封閉容器內加熱食物,所產生的熱量不容易散發,故會使容器內壓力過高,而引起爆破事故。故加熱液體時應使用廣口容器。即使在煎煮帶殼食物時,也要事先用針或筷子將殼刺破,以免加熱後引起爆裂、飛濺弄髒爐壁,甚或濺出傷及人身。

忌超時加熱:食品放入微波爐解凍或加熱,若忘記取出,如果時間超過2小時,則應丟掉不要,以免引起食物中毒。 忌將肉類加熱至半熟後再用微波爐加熱:因為在半熟的食品中細菌仍會生長,第二次再用微波爐加熱時,由於時間短,不可能將細菌全殺死。冰凍肉類食品須先在微波爐中解凍,然後再加熱為熟食。 忌再冷凍經微波爐解凍過的肉類:因為肉類在微波爐中解凍後,實際上已將外面一層低溫加熱了,在此溫度下細菌是可以繁殖的,雖再冷凍可使其繁殖停止,卻不能將活菌殺死。已用微波爐解凍的肉類,如果再放入冰箱冷凍,必須加熱至全熟。

忌油炸食品:因高溫油會發生飛濺,導致火災。 如萬一不慎引起爐內起火時,切忌立即開門,應先關閉電源,待火熄滅後,再開門降溫。 忌將微爐置於臥室,且不要用任何物品覆蓋微波爐上的散熱窗柵。 忌長時間在微波爐前工作:開啟微波爐後,人應遠離微波爐至少在1米以上的距離。

市售微波爐常見的規格 商品名稱 LG微波爐 規格型號 MG-5000MV1 品 牌 LG 微波輸入功率 1050W 容 量 20L 外觀尺寸 品 牌 LG 微波輸入功率 1050W 容 量 20L 外觀尺寸 483*285*360mm 微波輸出功率 700W 燒烤功率 900W 操作方式 電腦式 內膽材質 抗菌內膽 簡 介 *多重微波均勻加熱系統 * 耐高溫抗菌健康內膽 * 營養保存自動烹調功能表 * 時尚LED顯示 * 易清潔觸摸式控制面板 * 新型手拉門 * 多重防洩漏安全保護    

Lots More Information How Espresso Machines Work Related HowStuffWorks Articles in web site: http://home.howstuffworks.com/ How Espresso Machines Work How Food Processors Work How Grills Work How Radio Works How the Radio Spectrum Works

More Great Links J. Carlton Gallawa: How Does A Microwave Oven Work? Virginia.edu: Microwave Ovens Unwise Microwave Oven Experiments Food Safety, Preparation and Storage Tips: Microwave Cooking Microwave Engineering Online