High School Physics Eddy Current Electromagnetic Damping, High School Physics Eddy Current

Magnetic flux is not the same. To put it briefly, first, some magnetic inductance lines only pass through the upper ring, not through the lower ones; Second, the magnetic inductance lines are sparse and the corresponding magnetic inductance intensity is different, and the magnetic inductance lines passing through the ring below are more sparse, and the magnetic inductance intensity is smaller. It can be seen that the magnetic flux of the lower ring is smaller than that of the upper one.

According to Lenz's law or the law of electromagnetic induction, it can be judged that the generation of the induced electric field should hinder the change of magnetic flux, so electromagnetic damping is generated.

The magnetic flux of the two rings is the same.

No, the degree of density is different, and you can't use your sketch to judge.

Not all metals have a binding effect on magnetic inductance lines, only ferromagnets have this effect. Aluminum is not a ferromagnet. I don't know if I talked about ferromagnets in high school, but simply put, ferromagnets are metals that can be attracted to magnets. Aluminum obviously can't be attracted to magnets.

At university, it is said that ferromagnets are substances with great permeability, in which magnetic lines are trapped in the matter like the total reflection of light. Aluminum belongs to paramagnets, and its (permeability-1) is on the order of minus 5 of 10, while vacuum has a permeability of 1It can be seen that the permeability of aluminum is very close to that of a vacuum.

Therefore, the thin aluminum tube can only cause a small distortion of the magnetic inductance line, and the magnetic inductance line can be considered to be the same as that without the aluminum tube in the qualitative analysis.

It should be understood that induction cookers use eddy currents to work. Theoretically, whether it is an iron pot, an aluminum pot or a copper pot, it will produce eddy currents and can work. However, their efficiency varies widely.

The main reason is the eddy current of the induction cooker, which comes from the induced voltage generated by the changing magnetic field at the bottom of the pot.

Although the resistivity of aluminum and copper pots is small, the induced voltage generated by them is smaller with the same electromagnetic rate of change. On the other hand, because the relative permeability of the iron pot is large (about 1,000 times larger than that of copper and aluminum), the induced voltage generated is high, and even if the resistivity of the iron is large, there will be a large eddy current that converts electromagnetic energy into heat energy. Obviously, people prefer to use iron pots with high conversion efficiency to make induction cooker pots.

This statement is incorrect.

Induction cooker is the use of alternating magnetic field to make the molecules in the bottom of the pot material produce "molecular eddy current", which is related to the material, not a problem of resistivity, aluminum and copper can not be used as the bottom material of the induction cooker because of the relationship of molecular structure.

Take a look at the books on magnetic materials.

It has nothing to do with resistivity, mainly because their magnetic permeability is small, and they cannot concentrate the magnetic induction wires into the pot, so the induction current generated is small and not enough to generate enough heat. The magnetic permeability of iron is large, so iron pots are used.

Iron can conduct magnetism, and when the iron pot is placed on the induction cooker, the wire reel in the induction cooker will change greatly. After the machine is turned on, the current detection circuit in the machine detects a large current change, and the induction cooker works.

Aluminum and copper can not be magnetically conducted, when placed on the induction cooker, the wire reel.

Not much has changed. After the machine is turned on, the current detection circuit cannot detect a large current, so it is considered that there is no pot and does not work.

When the coil rotates in the magnetic field, the magnetic flux of the aluminum frame changes, so as to produce the induced current of the intelligent matter, and the ampere resistance appears, so that it will soon stop moving before the swing and the plastic skeleton can not achieve the effect of electromagnetic damping, the purpose of this is to use eddy currents to play the role of electromagnetic damping;

Therefore, I chose: BC