High score to solve the problem of electromagnets, questions about electromagnets

1) The efficiency of the electromagnet from electrical energy to attraction is about 45%.

2) The higher the AC solenoid coil at both ends of the magnetic pole, the higher the efficiency at both ends!

3) Of course there are DC solenoids. (such as electromagnetic chuck crane) 4) AC solenoid core is best stacked with silicon rigid sheets, (eddy current can be reduced) coil winding is the same as transformer! It's just that the number of laps per volt is doubled!

Find an iron rod, a little copper wire, the kind with insulating paint (you can remove the copper wire from the small motor, but don't scratch the wire), two batteries.

1. Scrape off the insulating paint at both ends of the copper wire.

2 Start from one end of the iron rod and go to the other end of the wire (single-strand copper wire), the line looks like a spring 3, after Rao to the other end, the two ends of the copper wire can be connected to direct current.

My opinion is different from the third floor.

The AC electromagnet is to short circuit the magnetic circuit, just like the contactor has two magnetic shorts, so that its magnetic force has only one direction, that is, it will not vibrate, and the core silicon steel sheet should be used as the core, and magnetic short-circuits should be added at both ends. There is no limit to how the wire can be wound.

Efficiency? It depends on how you do it, the permeability of the material, and the way the wire is wound. Also, do you want to communicate?

I don't know, it's just that the steel bar is magnetized back and forth like this, is there any effect? At most, you convert the AC to DC for reuse, such as rectifying with a thyristor (diode) or something.

Here's all the information!

All in English, click on the first clickable place to change to Chinese).

Categories: Education Science >> Science & Technology >> Engineering Technology Science Problem Description:

When an electromagnet is energized, it will not be short-circuited as if it was directly energized with a wire with the same resistance value, which is the reason why the magnetic field force hinders the passage of current? Can we treat this force that holds back the current as a resistor? If so, will the resistance value of this resistor change?

If it changes, what is the law of change?

Analysis: That's an interesting question. Here's how it works:

Since energized wires generate a magnetic field, the magnetic field, in turn, reacts to the change in current. Once the wire is wound into a coil and an alternating current is fed, the magnetic field generated by the coil wire will hinder the change of current, just like resistance, this phenomenon is called inductance. In physics, the magnitude of the inductive resistance is represented by l, and the formal name is inductive reactance, which is the angular velocity of the current change, and l is the inductance value of the coil.

In addition to the number of turns of the coil, whether there is an iron core inside and the size of the core, the size of the inductive reactance is also related to the frequency of the incoming alternating current, the larger the frequency, the greater the inductive reactance.

It is important to note that the coil has an inductive effect only when AC power is fed, and if DC is fed, then the coil is like a slender wire, and only the resistance works.

1. Question: What factors are related to the magnetic force of the electromagnet?

Hypothesis: It is related to the number of coil turns, the number of coil turns is large, and the magnetic force is large; The number of coil turns is small, and the magnetic force is less.

Constant condition: the number of cells of the thickness of the nails.

Condition of change: number of coil turns.

Experiment log. The conditions that change, the conditions that remain unchanged, the number of paper clips sucked into the first coil 20 turns, 2 batteries 6, the second coil 30 turns 2 batteries, and 8 batteries.

The third coil is 40 turns, 2 cells, and 10 batteries.

Our conclusion: the magnetic force of the electromagnet is related to the number of turns of the coil, and the more turns of the coil, the greater the magnetic force; The number of coil turns is small, and the magnetic force is less.

2. Question: What factors are related to the magnetic force of the electromagnet?

Hypothesis: It is related to the number of cells, the number of batteries is large, the magnetic force is large, the number of batteries is small, and the magnetic force is less.

Constant condition: the number of turns of the coil of the nail thickness.

Condition of change: number of batteries.

Basic Information.

It is a device that generates electromagnetism by energizing. A conductive winding that matches its power is wound around the outside of the core, and the coil that is emung with current is magnetic like a magnet, and it is also called an electromagnet. We usually make it into a bar or hoof shape to make the core more easily magnetized.

In addition, in order to degauss the electromagnet immediately when the electromagnet is deenergized, we often use soft iron or silicon steel materials that demagnetize quickly. Such an electromagnet is magnetic when energized, and the magnetism disappears when the power is off. Electromagnets have an extremely wide range of applications in our daily life, and the power of generators has been greatly improved due to its invention.

Chinese name. The foreign name of the electromagnet.

electromagnet

Discipline Science. The principle is that electromagnetism is generated.

Category 1AC solenoid 2DC solenoids.

1.Magnetic field lines are not real lines, they were introduced to describe the magnetic field vividly, and what really exists is the magnetic field.

2.The magnetic field is invisible, but we can know its existence by other means, such as the moving charge moving in the magnetic field will be affected by the magnetic field force and the motion will gain acceleration.

3.Permanent magnets are not always unconsumed, and it is clear from the structure of the magnet. The magnet is composed of magnetic domains, the so-called magnetic domains are small "paddy fields" with magnetic moments, when these small "paddy fields" are arranged in a certain regularity, the magnetic moments do not cancel each other, and they show magnetism outward.

After a long period of use, or heat, or impact, these small "paddy fields" are arranged in a disorderly manner, and the magnetism disappears.

4.The reason why small paddy fields have magnetic moments is because of the electronic structure of the atoms that make up the small paddy fields, and for elemental materials, such as iron, cobalt, nickel, etc., and compounds such as ferrite, after they are magnetized, the magnetic domains are regularly arranged, and they will show magnetism to the outside world.

5.The magnetic field generated by the magnet is not a closed field, it fills the whole space, but the magnetic field weakens so far away from it that it cannot be measured.

6.The closed conductor coil cuts the magnetic induction wire to produce electricity, which is the conversion of mechanical energy into electrical energy, and the energy is conserved. In this process, the external force has to do mechanical work on the coil, and the generated induced current will be hindered by the magnetic field force in turn (Lenz's law), and the magnetic field plays an intermediary role, because the free electrons in the coil are moved in the magnetic field and are affected by the magnetic field force to produce directional motion, thus forming the induced current.

It also involves exchange effects, etc., which can only be understood by studying university knowledge such as quantum mechanics.

1.First of all, the magnetic field line is an imaginary line, it does not exist. It is mainly used to facilitate our description of the nature of the magnetic field (magnitude, direction) in space.

2.The reason why permanent magnets always have a magnetic field is because they are not like other magnetic materials that do not exhibit magnetism. The magnetic moments inside it are arranged in an orderly manner rather than completely out of order. Just like tug-of-war, forces are exerted in one direction.

3.The magnetic field is due to the molecular current.

4.For metal coils, cut magnetic field wires to generate electricity. You can imagine hydroelectric power, which is the conversion of the mechanical energy of water into electrical energy; In the case of wind turbines, wind energy is converted into electricity. Conservation of energy is all the case that is satisfied.

Don't think that if you can't see it, you don't exist. The light visible to the human eye (electromagnetic waves) is finite, and given that between infrared and ultraviolet rays, the presence of magnetic field lines can be shown with metal powder.

It works.

You've drawn a cuboid, so use a cuboid.

4.But there's no need to think about turns in your head. Coil thickness. Because there is a universal **. Search for "permanent magnets", "electromagnets", and a large number of various models are available for you to choose from.

5.Since one is a permanent magnet, the force of pushing and pulling is of course only related to the electromagnet. The number of coils of the electromagnet is fixed, so the only variable value left is voltage.

As for "what does the force of pushing and pulling have to do with distance"? I'm sorry, but I don't know how big a permanent magnet you use, how big an electromagnet, and how much track damping you use, so I can't answer the question "What is the relationship between the force of pushing and pulling and the distance?"

And there's another thing you overlook, and that's the "power supply". If you play with dry batteries, the cost is basically the same as Xi Du. So you also have to buy a power supply, a switching power supply or an adjustable power supply.

I used to want to make an electromagnet like you, and I naively thought that I was looking for an iron rod, looking for a wire more than two meters long, and I thought it would be OK after more than 20 circles, but as soon as I connected the No. 1 dry battery (series connection) of 3V, it was instantly short-circuited and hot. Later, I consulted the teacher, and the teacher said, first of all, the wire is too short, resulting in the resistance value is too small, and connecting it is basically equal to a short circuit. Secondly, the wire must be wound very well, not blindly closed eyes to finish winding.

This device is feasible, but it is recommended that you change the permanent magnet to soft iron + spring, attract by electromagnets, return by springs, and can also do reciprocating motion;

The core is made of laminated silicon steel sheet, horseshoe-shaped, and the power supply is 220V alternating current, and the switch is controlled on and off;

Enameled wire for coil, 1000 turns;

The force of pushing and pulling is directly proportional to the square of the distance.

It's more complicated and requires a transformer.

Method 1: Use the right-hand spiral rule, according to the current you provide, you can determine that the magnetic field of the current is pointed out of the paper, and the magnet in it is balanced in the same direction as the current magnetic field, that is, the vertical paper is pointing out of the paper.

Method 2: Analyze a section of wire in the magnetic field at the n pole of the magnet, according to the left-hand rule, it can be seen that the wire is subjected to the force of the perpendicular paper surface pointing to the paper, because the force is opposite to the force, the n pole is subjected to a force that is perpendicular to the outside of the paper, and finally the n pole will be pointed to the outside of the paper.

Therefore b is right.

Answer: B

The Ampere's rule is used to determine that the magnetic field at the magnetic needle is perpendicular to the outward facing of the paper, so N turns outward and the S pole turns inward.

If the wire is wound around this nail, it is not a short circuit (besides, if you look at the textbook, the concept of short circuit is theoretical, that is, the wire is an ideal connection state with no resistance, no distributed inductance, and no distributed capacitance). If the insulated wire is wound, it is an inductor, and if there is an iron core in the coil, it is an electromagnet, which is an electrical device.

If you want to reduce power consumption, you can improve the conversion efficiency and reduce the current. It is possible to use longer wires to be wound around iron nails, which increases the resistance and the inductance.

1 To put it bluntly, electrical appliances are resistors. As long as the resistance of the nail is large enough, it is fine.

2 should be able q=i squared r i=u r r big i small, then squared will be smaller.