Name: 電子レンジの仕組み (How a Microwave Oven Works)
Uploaded: 2021-01-14T06:24:40.000Z
Duration: 5 min 12 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

﻿How a Microwave Oven Works EngineerGuy Series #4

This microwave oven is a truly remarkable feat of engineering.

関係詞節（制限と非制限）

The rapid heating that makes microwaves popular

Now, if you picture a vacuum tube at all it’s likely in

Inevitably, tiny transistors and microchips replaced

clunky vacuum tubes, but it's too soon to

Microchips can’t easily replace tubes for producing power.

Now, a microwave contains three main components

A waveguide hidden in the wall to direct that energy to the food

and a chamber to hold the food and safely contain the microwave radiation.

In principle, a microwave oven heats no differently

At a molecular level heat is a transfer of energy

that results in increased motion of the molecules in a substance.

In a traditional oven or stove we heat food

or in the oven where the walls radiate heat,

The insides cook when heat transfers from the surface

In contrast, energy from the magnetron penetrates

into the food, which means the whole mass of the food

we expose it to electromagnetic waves that emanate from the tube.

By definition, the waves have electrical and magnetic fields

For this oven, the direction of the fields change

two point four five billion times per second.

Water will try to align with the radiation’s electric field.

The changing field rocks the water molecules

back and forth rapidly and molecular friction

from this creates heat as the motion disrupts

the hydrogen bonds between neighboring water molecules.

Now, you can get an idea of the wavelength of the energy

Now, you can see on here sections where the cheese

has completely melted, and other sections where it’s completely unheated.

The oven’s metal walls only reflect waves of

This standing wave causes hot and cold spots inside the oven.

The three-dimensional pattern of waves is difficult to predict,

but the principle can be seen by looking at

The peaks and valleys in the wave represent

while the nodes here correspond to the "cold" spots inside the chamber.

If I measure the distance between melted cheese spots

and is pretty close to the actual wavelength of microwave radiation used.

Using that wavelength I can estimate the microwave radiation's frequency.

The frequency is related to the wavelength by the speed of light.

I get an answer that only has a 4 or 5 percent error.

Now, the real engineering in the microwave oven

It's truly an amazing and revolutionary device.

thin pieces of metal that dissipate the heat as the magnetron operates.

Now I have another one so you can see the inside.

the inner filament and the circular cooper outside.

This voltage “boils” electrons off the center filament

and they fly toward the circular copper section.

The filament is made from tungsten and thorium.

Tungsten because it can withstand high temperatures

and thorium because it’s a good source of electrons.

The magnets bend these electrons so they swing

We adjust the magnetic strength so that the now

orbiting electrons just brush past the opening of these cavities.

Like blowing over a half filled pop bottle to make it whistle,

this creates an oscillating wave - the microwave radiation that heats food.

It’s simply astonishing that these cavities can be made

with high precision, low cost, and incredibly high reliability.

This video is based on a chapter in the book

The chapter features more information about this subject.

Learn more about the book at the address below.