An electromagnet creates a magnetic field through a coil of electric current. In order to strengthen this field and direct the magnetic flux along a certain path, most electromagnets have a magnetic core made of soft magnetic steel.
Application of electromagnets
Electromagnets have become so widespread that it is difficult to name an area of technology where they are not used in one form or another. They are found in many household appliances - electric shavers, tape recorders, televisions, etc. Communication devices - telephony, telegraphy and radio - are unthinkable without their use.
Electromagnets are an integral part of electrical machines, many industrial automation devices, control and protection equipment for various electrical installations. A developing area of application for electromagnets is medical equipment. Finally, giant electromagnets for acceleration elementary particles used in synchrophasotrons.
The weight of electromagnets ranges from fractions of a gram to hundreds of tons, and the electrical power consumed during their operation ranges from milliwatts to tens of thousands of kilowatts.
A special area of application for electromagnets is electromagnetic mechanisms. In them, electromagnets are used as a drive to carry out the necessary translational movement of the working body or rotate it within a limited angle, or to create a holding force.
An example of such electromagnets are traction electromagnets, designed to perform specific work when moving certain working parts; electromagnetic locks; electromagnetic clutches and braking couplings and brake electromagnets; electromagnets actuating contact devices in relays, contactors, starters, circuit breakers; lifting electromagnets, vibrator electromagnets, etc.
In a number of devices, along with electromagnets or instead of them, permanent magnets are used (for example, magnetic plates of metal-cutting machines, braking devices, magnetic locks, etc.).
Classification of electromagnets
Electromagnets are very diverse in design, which differ in their characteristics and parameters, so the classification facilitates the study of the processes occurring during their operation.
Depending on the method of creating magnetic flux and the nature of the current magnetizing force, electromagnets are divided into three groups: neutral DC electromagnets, polarized DC electromagnets and alternating current electromagnets.
Neutral electromagnets
In neutral DC electromagnets, the working magnetic flux is created using a DC winding. The action of the electromagnet depends only on the magnitude of this flux and does not depend on its direction, and therefore, on the direction of the current in the electromagnet winding. In the absence of current, the magnetic flux and the attractive force acting on the armature are practically zero.
Polarized electromagnets
Polarized DC electromagnets are characterized by the presence of two independent magnetic fluxes: (polarizing and working). The polarizing magnetic flux is in most cases created using permanent magnets. Sometimes electromagnets are used for this purpose. The working flux occurs under the influence of the magnetizing force of the working or control winding. If the current is in they are absent, the attractive force created by the polarizing magnetic flux acts on the armature.The action of a polarized electromagnet depends on both the magnitude and the direction of the working flux, i.e., on the direction of the current in the working winding.
AC electromagnets
In AC electromagnets, the winding is powered from an AC source. The magnetic flux created by the winding through which alternating current passes periodically changes in magnitude and direction (alternating magnetic flux), as a result of which the force of electromagnetic attraction pulsates from zero to maximum at twice the frequency of the supply current.
However, for traction electromagnets, a decrease in the electromagnetic force below a certain level is unacceptable, since this leads to vibration of the armature, and in some cases to a direct disruption of normal operation. Therefore, in traction electromagnets operating with an alternating magnetic flux, it is necessary to resort to measures to reduce the depth of the force pulsation (for example, use a shielding coil covering part of the electromagnet pole).
In addition to the listed varieties, current-rectifying electromagnets are now widely used, which in terms of power supply can be classified as alternating current electromagnets, and in their characteristics are close to direct current electromagnets. Since there are still some specific features their work.
Depending on the method of switching on, the windings are distinguished electromagnets with series and parallel windings.
Series windings, operating at a given current, are made with a small number of turns of a large cross-section. The current passing through such a winding practically does not depend on its parameters, but is determined by the characteristics of the consumers connected in series with the winding.
Parallel windings, operating at a given voltage, have, as a rule, a very large number of turns and are made of small cross-section wire.
By nature of the winding electromagnets are divided into those operating in long-term, intermittent and short-term modes.
By speed of action electromagnets can be with normal speed actions, fast-acting and slow-acting. This division is somewhat arbitrary and mainly indicates whether special measures have been taken to obtain the required speed of action.
All of the above characteristics leave their mark on the design features of electromagnets.
Lifting electromagnets
Electromagnet device
At the same time, with all the variety of electromagnets encountered in practice, they consist of basic parts with the same purpose. These include a coil with a magnetizing winding located on it (there may be several coils and several windings), a stationary part of the magnetic circuit made of ferromagnetic material (yoke and core) and a moving part of the magnetic circuit (armature). In some cases, the stationary part of the magnetic circuit consists of several parts (base, housing, flanges, etc.). A)
The armature is separated from the remaining parts of the magnetic circuit by air gaps and is a part of the electromagnet, which, perceiving the electromagnetic force, transmits it to the corresponding parts of the driven mechanism.
The surfaces of the moving or stationary part of the magnetic circuit that limit the working air gap are called poles.
Depending on the location of the armature relative to the remaining parts of the electromagnet, there are electromagnets with an external attracting armature, electromagnets with a retracting armature and electromagnets with an external transversely moving armature.
Characteristic feature electromagnets with external attractive armature is the external location of the armature relative to the winding. It is affected mainly by the working flow passing from the armature to the end of the core cap. The nature of the armature movement can be rotational (for example, a valve solenoid) or translational. Leakage flows (closed in addition to the working gap) in such electromagnets practically do not create traction force, and therefore they are sought to be reduced. Electromagnets of this group are capable of developing quite a large force, but are usually used with relatively small armature working strokes.
Feature electromagnets with retractable armature are the partial arrangement of the armature in its initial position inside the coil and its further movement into the coil during operation. The leakage fluxes of such electromagnets, especially with large air gaps, create a certain traction force, as a result of which they are useful, especially with relatively large armature strokes. Such electromagnets can be made with or without a stop, and the shape of the surfaces forming the working gap can be different depending on what traction characteristic needs to be obtained.
Electromagnets with retractable armature can develop forces and have armature strokes that vary over a very wide range, which makes them widespread.
IN electromagnets with an external transversely moving armature the armature moves across the magnetic lines of force, turning through a certain limited angle. Such electromagnets usually develop relatively small forces, but they allow, by appropriately matching the shapes of the poles and armature, to obtain changes in the traction characteristics and a high return coefficient.
In each of the three listed groups of electromagnets, in turn, there are a number of design variations associated both with the nature of the current flowing through the winding and with the need to ensure the specified characteristics and parameters of the electromagnets.
There are four fundamental forces of physics, and one of them is called electromagnetism. Conventional magnets have limited use. An electromagnet is a device that creates an electric current during the passage. Since electricity can be turned on and off, so can an electromagnet. It can even be weakened or strengthened by decreasing or increasing the current. Electromagnets find their use in a variety of everyday electrical appliances, in various industrial fields, from ordinary switches to spacecraft propulsion systems.
What is an electromagnet?
An electromagnet can be considered as a temporary magnet that functions with the flow of electricity and its polarity can be easily changed by changing Also the strength of an electromagnet can be changed by changing the amount of current flowing through it.
The scope of application of electromagnetism is unusually wide. For example, magnetic switches are preferred because they are less susceptible to temperature changes and are able to maintain rated current without nuisance tripping.
Electromagnets and their applications
Here are some of the examples where they are used:
- Motors and generators. Thanks to electromagnets, it has become possible to produce electric motors and generators that operate on the principle of electromagnetic induction. This phenomenon was discovered scientist Michael Faraday. He proved that electric current creates a magnetic field. Generator uses external force wind, moving water or steam rotates a shaft, which causes a set of magnets to move around a coiled wire to create an electric current. Thus, electromagnets convert other types of energy into electrical energy.
- Industrial use practice. Only materials made from iron, nickel, cobalt or their alloys, as well as some natural minerals, react to a magnetic field. Where are electromagnets used? One of the areas of practical application is metal sorting. Since the mentioned elements are used in production, iron-containing alloys are effectively sorted using an electromagnet.
- Where are electromagnets used? They can also be used to lift and move massive objects, such as cars before disposal. They are also used in transportation. Trains in Asia and Europe use electromagnets to transport cars. This helps them move at phenomenal speeds.
Electromagnets in everyday life
Electromagnets are often used to store information, as many materials are capable of absorbing a magnetic field, which can then be read to retrieve information. They find application in almost any modern device.
Where are electromagnets used? In everyday life, they are used in a number of household appliances. One of the useful characteristics of an electromagnet is that it can change with changes in the strength and direction of the current flowing through the coils or windings around it. Speakers, loudspeakers and tape recorders are devices in which this effect is realized. Some electromagnets can be very strong, and their strength can be adjusted.
Where are electromagnets used in life? The simplest examples are electromagnetic locks. An electromagnetic lock is used for the door, creating a strong field. As long as current passes through the electromagnet, the door remains closed. Televisions, computers, cars, elevators and photocopiers are where electromagnets are used, to name a few.
Electromagnetic forces
Strength electromagnetic field can be adjusted by changing the electrical current passing through the wires wrapped around the magnet. If the direction of the electric current is reversed, the polarity of the magnetic field also reverses. This effect is used to create fields in a computer's magnetic tape or hard drive for storing information, as well as in speaker speakers in radios, televisions, and stereo systems.
Magnetism and electricity
The dictionary definitions of electricity and magnetism are different, although they are manifestations of the same force. When they create a magnetic field. Its change, in turn, leads to the generation of electric current.
Inventors use electromagnetic forces to create electric motors, generators, toys, consumer electronics and many other invaluable devices without which everyday life is impossible to imagine. modern man. Electromagnets are inextricably linked with electricity; they simply cannot work without an external power source.
Application of lifting and large-scale electromagnets
Electric motors and generators are vital in modern world. The motor takes electrical energy and uses a magnet to convert electrical energy into kinetic energy. A generator, on the other hand, converts motion using magnets to generate electricity. When moving large metal objects, lifting electromagnets are used. They are also necessary when sorting scrap metal, to separate cast iron and other ferrous metals from non-ferrous ones.
A real miracle of technology is a Japanese levitating train capable of reaching speeds of up to 320 kilometers per hour. It uses electromagnets to help it float in the air and move incredibly fast. The US Navy is conducting high-tech experiments with a futuristic electromagnetic rail gun. She can direct her projectiles over considerable distances with great speed. The projectiles have enormous kinetic energy, so they can hit targets without the use of explosives.
The concept of electromagnetic induction
When studying electricity and magnetism, an important concept is when a flow of electricity occurs in a conductor in the presence of a changing magnetic field. The use of electromagnets with their induction principles are actively used in electric motors, generators and transformers.
Where can electromagnets be used in medicine?
Magnetic resonance imaging (MRI) scanners also operate using electromagnets. This is a specialized medical method for examination internal organs people who are not available for direct examination. Along with the main one, additional gradient magnets are used.
Where are electromagnets used? They are present in all types of electrical devices, including hard drives, speakers, motors, and generators. Electromagnets are used everywhere and, despite their invisibility, occupy an important place in the life of modern man.
Along with permanent magnets, since the 19th century, people began to actively use variable magnets in technology and everyday life, the operation of which can be regulated by the supply of electric current. Structurally, a simple electromagnet is a coil of electrical insulating material with a wire wound on it. If you have a minimum set of materials and tools, it is not difficult to make an electromagnet yourself. We will tell you how to do it in this article.
When electric current passes through a conductor, a magnetic field appears around the wire; when the current is turned off, the field disappears. To enhance the magnetic properties, a steel core can be introduced into the center of the coil or the current can be increased.
Use of electromagnets in everyday life
Electromagnets can be used to solve a number of problems:
- for collecting and removing steel filings or small steel fasteners;
- in the manufacturing process various games and toys together with children;
- for electrifying screwdrivers and bits, which allows you to magnetize screws and facilitate the process of screwing them;
- for conducting various experiments on electromagnetism.
Making a simple electromagnet
The simplest electromagnet, quite suitable for solving a small range of practical household problems, can be made with your own hands without using a coil.
For work, prepare the following materials:
- steel rod with a diameter of 5-8 millimeters or a 100 nail;
- copper wire in varnish insulation with a diameter of 0.1-0.3 millimeters;
- two pieces of 20 centimeters of copper wire in PVC insulation;
- insulating tape;
- source of electricity (battery, accumulator, etc.).
From tools, prepare scissors or wire cutters (side cutters) for cutting wires, pliers, and a lighter.
The first stage is winding the electrical wire. Wind several hundred turns of thin wire directly onto the steel core (nail). Carrying out this process manually takes quite a long time. Use a simple winding device. Clamp the nail into the chuck of a screwdriver or electric drill, turn on the tool and, guiding the wire, wind it. Wrap pieces of larger diameter wire to the ends of the wound wire and insulate the contact points with insulating tape.
When operating the magnet, all that remains is to connect the free ends of the wires to the poles of the current source. The distribution of connection polarity does not affect the operation of the device.
Using the switch
For ease of use, we suggest slightly improving the resulting diagram. Two more elements should be added to the above list. The first of them is the third wire in PVC insulation. The second is a switch of any type (keyboard, push-button, etc.).
Thus, the electromagnet connection diagram will look like this:
- the first wire connects one contact of the battery to the contact of the switch;
- the second wire connects the second contact of the switch with one of the contacts of the electromagnet wire;
the third wire completes the circuit, connecting the second contact of the electromagnet to the remaining contact of the battery.
Using a switch, turning on and off the electromagnet will be much more convenient.
Coil based electromagnet
A more complex electromagnet is made on the basis of a coil of electrical insulating material - cardboard, wood, plastic. If you don’t have such an element, it’s easy to make it yourself. Take a small tube from the indicated materials and glue a couple of washers with holes to it at the ends. It is better if the washers are located at a small distance from the ends of the coil.
Hi all! Today I am going to tell you about a very easy but spectacular experiment, and its name is: “Electromagnet”! I’m more than sure that every novice radio amateur knows it, but for starters it’s just right. I made this homemade review for those who are interested in how a magnet works.
Before the instructions, let's look at the operating principle of an electromagnet. What Wikipedia tells us:
An electromagnet is a device that creates a magnetic field when an electric current passes through it. Typically, an electromagnet consists of a winding and a ferromagnetic core, which acquires the properties of a magnet when an electric current passes through the winding.
- Unclear? Let me explain simply:
- Where are electromagnets used:
Strong electromagnets are used in different mechanisms for different purposes. For example, an electromagnetic crane is used in metallurgical and metal processing plants to move scrap metal and finished parts. Factories often work with machines that are also called “magnetic tables”, on which you can work with iron or steel products that are fixed with magnets using powerful electromagnets. You only need to turn on the current to firmly secure the part in any desired position on the table, turn off the current to release the product. When packaging magnetic ores from non-magnetic ones, for example, when cleaning pieces of iron ore from waste rock, magnetic separators are used, in which the ore being purified passes through a powerful magnetic field of electromagnets, which collects all the magnetic elements from it.
We will need:
- Iron nail
- Thin insulated wire (the more the better)
- Battery (any power, not less than 1.5V)
- Objects for testing a magnet (paper clips, buttons, pins)
- Wire Stripper (Optional)
- Adhesive tape
Safety regulations:
- Do not try to connect wires to a 220V outlet. Our electromagnet uses electricity, and when you connect it to standard high voltage, you will short circuit the entire house.
- You should have plenty of free wire up to the battery. If this happens, you will not have a strong electrical resistance, and the battery will self-destruct!
- Our electromagnet only needs low voltage. If you will be using high voltage
you will receive an electric shock.
And now to the instructions:
1.Wrap the copper wire around the nail, but so that there is about 30 cm left at each end, make sure that the wire is twisted only in one direction or you will have two small fields that will interfere with each other. IMPORTANT: The wire must be wound so that it lies not far from the previous skein, but is not on top of it.
Hint: The more layers, the stronger the magnet, you can even make a multi-layer one.
2.Now let's clean the ends of the copper wire (about 3 cm), preferably done with a wire cleaning device. They need to be cleaned for better current flow. After peeling, the ends will look lighter than unpeeled ends.
3.Take one end of the wire and connect it to the positive side of the battery, and then glue them together with adhesive tape so that they touch each other. And if we press with our finger, we will launch the magnet.
IMPORTANT: The wire and plus batteries must be connected at all times.
What we did: We connected the contacts into one circuit (essentially a short circuit) and form a magnetic field (I already wrote about this above). To turn it off, you need to release the wire.
An electromagnet is a magnet that works (creates a magnetic field) only when electric current flows through a coil. To make a powerful electromagnet, you need to take a magnetic core and wrap it with copper wire and simply pass current through this wire. The magnetic core will begin to be magnetized by the coil and begin to attract iron objects. If you want a powerful magnet, increase the voltage and current, experiment. And so as not to have to worry about assembling the magnet yourself, you can simply remove the coil from the magnetic starter (they come in different types, 220V/380V). You take out this coil and insert a piece of any piece of iron inside (for example, an ordinary thick nail) and plug it into the network. This will be a really good magnet. And if you don’t have the opportunity to get a coil from a magnetic starter, then now we’ll look at how to make an electromagnet yourself.
To assemble an electromagnet, you will need wire, a DC source, and a core. Now we take our core and wind copper wire around it (it’s better to turn one turn at a time, not in bulk - the efficiency will increase). If we want to make a powerful electromagnet, then we wind it in several layers, i.e. When you have wound the first layer, go to the second layer, and then wind the third layer. When winding, keep in mind that what you are winding, that coil has reactance, and when flowing through that coil, less current will flow with more reactance. But also keep in mind that we need and important current, because we will use current to magnetize the core, which serves as an electromagnet. But a large current will greatly heat the coil through which the current flows, so correlate these three concepts: coil resistance, current and temperature.
When winding the wire, select the optimal thickness of copper wire (about 0.5 mm). Or you can experiment, taking into account that the smaller the cross-section of the wire, the greater the reactance will be and, accordingly, the less current will flow. But if you wind with a thick wire (about 1mm), it would not be bad, because the thicker the conductor, the stronger the magnetic field around the conductor and, on top of that, more current will flow, because the reactance will be less. The current will also depend on the frequency of the voltage (if on alternating current). It’s also worth saying a few words about layers: the more layers, the greater the magnetic field of the coil and the stronger the core will magnetize, because When layers are superimposed, the magnetic fields add up.
Okay, the coil has been wound and the core has been inserted inside, now you can start applying voltage to the coil. Apply voltage and begin to increase it (if you have a power supply with voltage regulation, then gradually increase the voltage). At the same time, we make sure that our coil does not heat up. We select the voltage so that during operation the coil is slightly warm or just warm - this will be the nominal operating mode, and you can also find out the rated current and voltage by measuring on the coil and find out the power consumption of the electromagnet by multiplying the current and voltage.
If you are going to turn on an electromagnet from a 220-volt outlet, then first be sure to measure the resistance of the coil. When a current of 1 Ampere flows through the coil, the coil resistance should be 220 ohms. If 2 Amps, then 110 Ohms. This is how we calculate CURRENT = voltage/resistance = 220/110 = 2 A.
That's it, turn on the device. Try holding a nail or a paper clip - it should attract. If it is poorly attracted or holds very poorly, then wind up five layers of copper wire: the magnetic field will increase and the resistance will increase, and if the resistance increases, then the nominal data of the electromagnet will change and it will be necessary to reconfigure it.
If you want to increase the power of the magnet, then take a horseshoe-shaped core and wind the wire on two sides, so you get a horseshoe lure consisting of a core and two coils. Magnetic fields two coils will add up, which means the magnet will work 2 times more powerful. The diameter and composition of the core plays a big role. With a small cross-section, we will get a weak electromagnet, even if we apply high voltage, but if we increase the cross-section of the heart, then we will get a not bad electromagnet. Yes, if the core is also made of an alloy of iron and cobalt (this alloy is characterized by good magnetic conductivity), then the conductivity will increase and due to this the core will be better magnetized by the field of the coil.
Conclusions:
- If we want to assemble a powerful electromagnet, then we wind the maximum number of layers (the diameter of the wire is not so important).
- It is best to take a horseshoe-shaped core (you will only need to power the 2nd coils).
- The core must be an alloy of iron and cobalt.
- If possible, the current should flow as much as possible, because it is this that creates the magnetic field.
