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Practice Listening: Select Missing Word
ID: #39951
Medium
Microwave
Transcript:
In a microwave oven, an electronic vacuum tube called a magnetron produces short radio waves called microwaves. In most such ovens, these waves travel through a waveguide, a rectangular metal tube, to a stirrer, a fan-like device that scatters the waves around the metal interior of the oven. The waves bounce from wall to wall until they enter the food. Water molecules, which are contained in most foods, are dipolar. That is, they have a positive electrical charge at one end and an equal negative charge at the other. These dipolar molecules act as tiny magnets and as microwaves pass into the food, the molecules are pulled first one way, then the other by a magnetic field created by the waves. This back and forth motion of the molecules occurs nearly 2 1/2 billion times a second. This rapid vibration causes friction between the water molecules, which produces (heat).
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