Development history
During the Second World War (1945), Spencer, an American radar engineer, happened to find the chocolate bar in his pocket melted and sticky while doing radar experiments. He suspected that it was caused by his body temperature, and later he found the thermal effect of microwave in continuous experiments.
Using this thermal effect, the United States issued a 1 patent on microwave in 1945, and Raytheon Company of the United States developed the world's first 1 microwave oven in 1947. In the 1940s, microwave ovens were mainly used in industry and commerce.
After people's continuous improvement, the household microwave oven was born in western Europe in 1955, and began to enter the family in the 1960s. In the 1970s, due to the problems of radiation safety and convenient operation, the cost of the microwave oven continued to drop, and it was further popularized and used, forming an important family industry, and at the same time, it was constantly improved in variety and technology.
In 1980s and 1990s, the continuous application of control technology and sensing technology made microwave ovens widely popular.
principle of operation
Microwave oven is a cooking appliance that uses food to absorb microwave energy in microwave field and heat itself. The microwave generated by the microwave generator in the microwave oven establishes a microwave electric field in the cavity of the microwave oven, and certain measures are taken to make this microwave electric field distributed as evenly as possible in the cavity of the microwave oven. Food is put into this microwave electric field, and the cooking time and microwave electric field intensity are controlled by the control center to carry out various cooking processes.
Generally speaking, microwave is a kind of high-frequency electromagnetic wave, which does not generate heat itself. There are microwaves everywhere in the universe and nature, but there are microwaves in nature. Because they are scattered and not concentrated, it is impossible to heat food.
Microwave ovens use their internal magnetrons to convert electric energy into microwaves, which penetrate food at an oscillation frequency of 2450MHz. When microwave is absorbed by food, polar molecules in food (such as water, fat, protein, sugar, etc. ) is attracted to oscillate rapidly at a speed of 2.45 billion times per second. The macroscopic manifestation of this oscillation is that food is heated.
Simply put, the principle of microwave heating is that when microwave is radiated to food, food always contains a certain amount of water, and water is composed of polar molecules (even if there is no external electric field, the positive and negative charge centers of molecules do not coincide), and the orientation of this polar molecule will change with the microwave field. Due to the movement of polar water molecules in food.
As well as the interaction between adjacent molecules, it produces a phenomenon similar to friction, which makes the water temperature rise, so the temperature of food also rises. The food heated by microwave is heated at the same time, so that the whole object is heated evenly and the heating speed is fast. It heats food 5 cm deep at a frequency of 2.45 billion times per second, accelerating the operation of molecules.
Baidu encyclopedia-microwave oven