How does the toaster work, is it just a simple electric resistance heating?

Release time:2019-06-24 Pageviews:
You return to the kitchen from the bathroom, cut the bagels in half and place them in the toaster, then press the toaster bar. The toaster's spring pushes the toasted bread piece up, and now the spring is compressed, causing the piece of bread to fall into the toaster.
The hot wire of the toaster began to heat up and eventually turned into a dazzling red color. The butter on the table is a bit hard. You put it in a butter dish and place the butter dish on the opening of the toaster. The heat generated by the toaster will make the butter softer and easier to apply. Toasters are not a recent invention in the United States, and their ancestors may not be familiar with toasters. When you put a piece of bread in the toaster and press the lever, you not only let the bread out of the toaster, but also close a circuit.
As soon as this circuit is closed, current flows through the heating wire near the bread. After about half a minute, the heating wire heats up and glows red. Why is this? To understand how a toaster converts electrical energy into heat and light, we must first understand the mechanics of thermodynamics, electromagnetism, and quantum mechanics. Yes, for a piece of toast, we have to learn so much knowledge! The toaster uses the first law of thermodynamics. This law tells us that in a closed system, the total amount of heat and work remains the same. When you press the pressure bar of the toaster, the circuit closes and a current is generated in the coil. Since the coil has resistance, the electrical energy of the current is converted into heat.
Let's take a look at the metal coil first. To be a good conductor of electricity, a material must have a large amount of charge that can move freely. The metal contains a high density of free charges, so the metal has good electrical conductivity. The charge in materials such as plastics and glass is bound by chemical bonds between atoms, so these materials are insulators. In a solid, the arrangement of atoms and the chemical interaction between atoms determine whether the material is an insulator or an electrical conductor. The arrangement of atoms and the chemical interaction between atoms are limited by quantum mechanics.
The electric heating wire of the toaster is generally made of an alloy of nickel and chromium (called nickel chrome). Both nickel and chromium metals are electrically conductive. A toaster wants to quickly heat the bread slices. The heating wire used must be a good conductor of electricity, but the electrical conductivity of the heating wire should not be too good. Mixing two different metals in a nickel-chromium electric heating wire, together with other imperfections, can help us achieve the desired effect of heating the bread.
We can imagine the electric wire of the toaster as a large staircase, and a group of people have to go down the stairs at the same time. The more people come out from the bottom step, the faster the group moves and the higher the current. In fact, the power to get these people down the stairs is voltage. In this analogy, we can also think of the voltage as the inclination of the stairs, and the steep stairs correspond to the higher voltage. When the stairs are steep, everyone will go downstairs quickly. Each step of the stairs corresponds to the atoms in the metal. To get a group of people down the stairs faster (especially when there are a lot of people), the best way is to let everyone line up along the stairs (according to the width of the steps) Lined up in a row, and then everyone walked downstairs in a step-by-step manner.
When a horizontal row of people walks down the last step, another horizontal row of people walks down the first step, so that the stairs can run at the highest efficiency. However, the people on the stairs do not act in unison, and their actions are somewhat random, just like the electrons in a wire. Moreover, the steps of a real staircase are not completely evenly distributed (the real wires are not). If there is a step missing on the stairs (this corresponds to the fact that the atom is not in the position where it is in the wire), and no one finds it before going to this step, it will make a big fall. . This situation leads to a drop in efficiency, and the process of going downstairs takes longer (the current in the heating wire of the toaster is also smaller).
In metals, the above situation leads to the generation of "resistance". It is more difficult to pass current through a long, thin wire than through a short, thick wire. In some devices, resistance is an obstacle that needs to be overcome. However, when we used the toaster for breakfast, the resistance was helping us. Since the wire has resistance, the kinetic energy of the current is transferred to the atoms in the wire. As the energy increases, the atoms vibrate more intensely. This process is called "Joule heating." For this reason, the toaster is made of nickel-chromium alloy to make the heating wire - this alloy has both certain electrical conductivity and large electrical resistance, thus ensuring the most Joule heat generated when the wire is energized.
If enough kinetic energy is transmitted to the atom, the atom will vibrate violently; if the atom vibrates sufficiently sharply, the heating wire will glow red. When the atom vibrates, the electron will sway like a heavy object hanging from the other end of the spring, and a changing current will be formed inside the atom. The magnitude and direction of the internal current of this atom is constantly changing, forming a constantly changing magnetic field, which in turn produces an electric field. Let us recall the charged pendulum ball mentioned earlier. The periodically changing electric and magnetic fields together form an oscillating electromagnetic wave, which is what we call "light."
In order to bake a piece of delicious bread, the heat of the heating wire (the temperature of the heating wire may exceed 538 degrees Celsius or 1000 degrees Fahrenheit) must be transferred to the bread. When the hair dryer and the electric heater work, the air molecules pass through the heating wire to obtain excessive kinetic energy on the heating wire. In the toaster, the heating process is mainly done by infrared rays. When the surface temperature of the bread reaches 149 degrees Celsius or 300 degrees Fahrenheit, the sugar and starch in the bread react chemically, and the taste and texture of the bread begin to change.
The toaster has a knob for adjusting the different heating positions. This knob actually controls an adjustable resistance that changes the current in the heating wire by changing the resistance.
In addition, the toaster has a timer or temperature sensor that will disconnect the closed circuit after a certain amount of time or temperature has been reached - this will prevent the bread from being baked. How about, I don’t want to start one, I want to buy one after I read it.