High frequency electromagnetic waves

In microwave drying, the product is exposed to very high-frequency electromagnetic waves. The transfer of these waves to the product is similar to the transfer of radiant heat. 

The electrons are heated by external high-power, high-frequency electromagnetic waves. The frequency is usually between 2.45 and 28 GHz (the most often used frequency is 14.5 GHz) and the applied MW power is several hundreds of watts, sometimes up to several kW. The cyclotron frequency of electrons is proportional to the magnetic flux density (see Eq. 50.3), that is, depends on the time-dependent position of the electron in the plasma. Because the... 

In microwave drying, the product is exposed to very high-frequency electromagnetic waves. The transfer of these waves to the product is similar to the transfer of radiant heat. As a result of high-frequency waves, water molecules are polarized and tend to change orientation. In the process of orientation, sufficient heat to expel moisture from the product is generated. 

Materials may be heated using high frequency electromagnetic waves in microwave oven. This heating arises from the interaction of electric field component of the wave with charge particle in the material. Two basic mechanisms are involved in the heating of materials. These are ... 

It heis long been established that a dielectric material, such as many types of ceramics, can be heated with energy in the form of high frequency electromagnetic waves. The frequency range used for microwave heating lies between 400 MHz and 40 GHz, however the allowed frequencies are restricted to distinct bands which have been allocated for Industrial, Scientific and Medical (ISM) use, as shown in Table 1. The principal frequencies are centred at 433 MHz, 915 MHz (896 MHz in the UK) and 2450 MHz since specific industrial equipment can be readily purchased. 

The frequency of microwave radiation lies between that of IR radiation and high frequency radio waves and the boundaries between these regions are not fixed [221]. The microwaves are generated in a transmitter (magnetron) which possesses a stalk which penetrates Uke a radio antenna into a hollow energy guide (Fig. 48). This leads the electromagnetic waves into the reaction chamber (power about... 

Experimental apparatus Electromagnetic emission source, electromagnetic energy meter (tesla), high frequency mechanical wave recorder, coal and rock strain recorder, methane, ethane, carbon monoxide sensors, data logger. 

Electrodeless devices are used to generate cold plasma, typically within a quartz tube by a high-frequency electromagnetic energy. A surface-wave applicator with longitudinal propagation of microwave energy is especially... 

In this work, a microwave interferometric method and apparatus for vibration measurements is described. The principle of operation is based on measurement of the phase of reflected electromagnetic wave changing due to vibration. The most important features of the method are as follows simultaneous measurement of tlie magnitude and frequency of the rotating object high measurement accuracy weak influence of the roll diameter, shape and distance to the object under test. Besides, tlie reflecting surface can be either metallic or non-metallic. Some technical characteristics are given. 

Figure 12.10 The electromagnetic spectrum covers a continuous range of wavelengths and frequencies, from radio waves at the low-frequency end to gamma (y) rays at the high-frequency end. The familiar visible region accounts for only a small portion near the middle of the spectrum.

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