The heated medium can be divided in

The heated medium can be divided into nonpolar molecular dielectric and polar molecular dielectric. Polar molecules do not show polarity without an applied electric field. If this medium is placed in an applied electric field, each polar molecule will form an orderly arrangement along the direction of the electric field force and will sense the opposite charge on the surface of the dielectric. This process is called polarization. The stronger the applied electric field, the stronger the polarization. When the applied electric field changes the direction, the polar molecules are arranged in the opposite direction. If the alternating electric field and magnetic field are applied, the polar molecules will be magnetized repeatedly. The higher the frequency of the alternating electric field, the faster the polarization of the polar molecules will turn repeatedly. At this time, the kinetic energy of molecular thermal motion increases, that is, the heat increases, and the temperature of food increases, so the conversion of electromagnetic energy to heat energy is completed. Domestic microwave ovens have a frequency of 2450 MHz, and the direction of the electric field changes 2.45 billion times per second, and the amount of heat generated is conceivable.