difference between permanent magnet and electromagnet | Linquip (2023)

The difference between permanent magnet and electromagnet is in their forces and fields. The magnetic field of a permanent magnet is always constant, but the electromagnetic magnetic field is created by the buildup of an electric current and ends when the current is removed.

The difference in strength between the two is due to the nature ofmagnetization🇧🇷 That is, when the magnetic property of the permanent magnet is greater, the magnet is stronger. But with the electromagnet, the strength depends on the electric current.

This article introduces both types of magnets and discusses the difference between a permanent magnet and an electromagnet.

Magnetic

Any object that creates a magnetic field is called a magnet. The magnetic field is invisible, but it has an absorbing effect on ferromagnetic materials such as iron, nickel, cobalt, etc. It also has an absorbing or repelling effect on other magnets.

magnetism

Magnets generally refer to objects that produce a stable magnetic field even when no magnetic field is applied to them. This is a characteristic of a certain category of materials. Obviously, most materials produce a magnetic field when a magnetic field is applied to them. This phenomenon is called magnetism, which has different types. Every substance exhibits at least one type of magnetism.

The magnetic behavior of a substance depends on its general structure and, in particular, on the arrangement of its electrons. The most well-known types of magnetic behavior of different materials are the following:

Ferromagnetic and Ferrimagnetic

Ferromagnetic and ferrimagnetic materials are those that are attracted to a magnet and can naturally become a magnet while maintaining its magnetization. Ferromagnetic and ferromagnetic materials are similar, but ferromagnetic materials are stronger than each other. The difference is in their internal structure.

Paramagnetic

Paramagnetic materials are substances that are very poorly absorbed by magnets, such as oxygen, platinum and aluminum. These materials cannot be magnetized. The absorption of these materials in magnets is a thousand times weaker than that of ferromagnetic materials.

diamagnético

Diamagnetic means repulsion by a magnet. These materials do not have magnetic properties. Examples of these materials are plastics, water, carbon and copper. Most materials fall into this category. Superconducting materials also fall into this category because they completely repel the magnetic field.

The figure below shows the magnetic behavior of various materials with and without the presence of a magnetic field.

Dauermagnet

Any object made of a magnetized material that can create a permanent magnetic field is a permanent magnet. Materials that are well attracted to the magnet are ferromagnetic materials as well as ferrimagnetic materials. Nickel, iron, cobalt and theirdiseasesbelong to these materials.

The use of permanent magnets is quite widespread in our daily life. Like a fridge magnet. Of course, many of the everyday uses of permanent magnets are invisible, but without them, many of our daily routines are impossible. Like the role of magnets in operating cars, imaging systems, generators, televisions, personal computers, telephones, and so on.

Strongly magnetized hard materials become permanent magnets. An example that fully describes the behavior of a permanent magnet is the bar magnet. Permanent magnets are also often called bar magnets.

Magnets are natural or artificial. Natural magnets, like magnets, inherently have a weak magnetic field. But artificial magnets are handmade, have a stronger field, and are made anyway suitable for human use.

The magnet has two poles: north pole and south pole. When we hang a magnet, the north pole is the pole that faces the Earth's magnetic north pole, and vice versa to determine the south pole of the magnet. If you break a bar magnet in half, it still has two poles, north and south. No matter how many times you continue this break, the two poles, north and south remain for her.

The strongest magnetic property is a magnet at its poles. If you place two bar magnets next to each other, like poles will repel and like poles will attract. A bar magnet will also pick up all ferromagnetic materials.

How is a permanent magnet made?

Permanent magnetism arises from the internal structure of a substance. Inside the atoms are the electrons and nuclei of the atoms, which are naturally magnetic and spin around like bits of electrical charge. Also by the rotation of the electron around the nucleus in theElectronic circuits, a magnetic field is created.

So, microscopically, the magnetic field of permanent magnets is the result of three factors: electron spins, nuclear spins and electron orbits.

Many materials do not have permanent magnetic properties because the magnetic fields of each of these factors point randomly in all directions and cancel each other out. But in ferromagnetic materials, the fields caused by the rotation of the nucleus and the electron and the circle of electrons add up, reinforcing each other and creating a permanent magnetic field.

The strength of a permanent magnet depends entirely on the internal structure of the material. The strongest permanent magnetic field has a strength of 8,000Gauss🇧🇷 Of course, up to 450,000 gauss have been obtained in the laboratory.

magnetic field lines

If we place the magnet on a piece of paper and sprinkle the iron filings around it, the position that the iron filings form around the magnet of the magnet represents the magnetic field lines. In fact, magnetic field lines are a series of hypothetical lines that represent the strength and orientation of the surrounding field and show the surrounding magnetic material.

Magnetic field lines have the following properties:

• These lines are closed and continuous.
• The tangent at each point represents the direction of the magnetic field at that point.
• Dense lines represent a stronger field.
• The magnetic field lines do not intersect.

types of permanent magnets

Types of permanent magnets include:

ceramic magnet

Ceramic magnets are the cheapest permanent magnets used in cases like food processing.

flexible magnet

These magnets can be made from a combination of polymers, plastics and magnetic powders. An example is the use of flexible magnets in refrigerator doors.

Neodymium Iron Boron Magnet

These types of magnets (NdFeB) are used to make jewelry. They are rare, expensive, and something of a magnet for the earth.

Imam of Samaria Cobalt

This is also a type of earth magnet. Therefore, it is rare and expensive, but resistant to oxidation, unlike NdFeB magnet. The use of this magnet (SmCo) is in turbomachines.

Properties of permanent magnets

• A permanent magnet generates a strong magnetic field even with a low mass.
• A good permanent magnet is resistant to demagnetization.
• A permanent magnet is used at a certain temperature. Therefore, they do not work properly on devices that operate at high temperatures.
• The corrosion resistance of a permanent magnet over time is low; therefore, its strength gradually decreases.
• The poles of a permanent magnet cannot be changed.

Electromagnet

An electromagnetic field is created by an electric current in a wire wound in a coil around a core of a ferromagnetic material, such as iron. A magnetic field is generated towards the center of the coil and the metal core increases its strength. When the electric current is removed, the magnetic field also disappears.

In the figure below you can see the direction of a magnetic field (B) generated by an electric current (I).

The formula for calculating the magnetic field generated by a current is as follows:

B=\frac{{\mu_{0}}I}{2{\pi}r}

{\mu_{0}}=4{\pi}\times 10^{-7}\frac{Tm}{A}

Tesla (T) is the unit of magnetic flux density (B) per unit cross-sectional area. Also, r is the radial distance from the supply wire.

The application of electromagnets in the electrical industry and mechanical engineering is very wide. For example, they are used in engines, generators, hard drives, loudspeakers, cranes for lifting heavy objects, and medical equipment like MRIs.

Electromagnets are used in transformers where the coils create alternating magnetic fields and supply the electrical current to induce the voltage. The most commonly used transformers in the electrical grid are used to control AC voltages.

According to Ampere's law, electric current in a wire creates a magnetic field around the wire. If several wires are wound next to each other, a strong central field will be created in the middle. A coil forming a straight tube is called a solenoid.

Ampère's Law states that the integral of the magnetic field strength (H) within a closed circuit is equal to the sum of the sum of the currents flowing through the circuit. In mathematical language it means:

\oint H.dL=\int J.dA

The right of the above equation can be written as the algebraic sum of the currents flowing through the loop.

\oint H.dL=I_{enc}

If we want to calculate the magnetic field in a ring of radius r, the above relationship can be written as:

2{\pi}rH=I_{enc}

or

H=\frac{I_{enc}}{2{\pi}r}

The direction of the magnetic field can be determined using the right-hand rule. In this way, when the fingers of the right hand are bent in the direction of the current in the coils, the thumb of the right hand is in the direction of the magnetic field. The direction from which the field lines run represents the North Pole.

The relationship between B and H is like the following relationship.

H=\frac{B}{{\mu}}-M

Here M and μ are magnetization and magnetic permeability, respectively.

It is necessary to mention Maxwell's equation, which explains the relationship between an electric field and a magnetic field.

{\nabla}\times \overrightarrow{E}=-\frac{{\partial}\overrightarrow{B}}{{\partial}t}

The magnetic flux density and electric field strength exert a force on a charge q moving with velocity v, which is explained by the Lorentz force equation.

\overrightarrow{F}=q(\overrightarrow{E}+\overrightarrow{v}\vezes \overrightarrow{B})

appliesStokes' theoremto Maxwell's equation leads to the following equation.

\oint E.dL=-\frac{{\partial}}{{\partial}t}\int \overrightarrow{B}.d\overrightarrow{A}

The integration of the electric field around a closed circuit leads to the definition of the electromotive force ζ. Also, Φ denotes the magnetic flux, the surface integral of the magnetic flux density surrounded by the loop.

{\zeta}=-\frac{\partial{\Phi}}{\partial{t}}

This is known as Faraday's law of electromagnetic induction, which states that when a conductor is in a changing magnetic field, there is an induction of an electromotive force.

magnetic core

If a core of ferromagnetic material is used in the center of the coil, the magnetic field can be amplified up to a thousand times due to the high permeability coefficient of the material. These types of electromagnets are called ferromagnetic cores or iron cores.

Of course, not all electromagnets are ferromagnetic core types, especially very powerful electromagnets like superconductors or those with very high currents in their coils cannot have a core.

The material used in the electromagnetic core has small areas called magnetic domains. Usually they are oriented in such a way that they cancel each other's magnetic effect and the object is not considered a magnet. But once a current is generated in the coil around the object, the resulting magnetic field aligns and parallelizes small magnetic areas.

The effect of the coil current field and the magnetic field increases in the same direction. This creates a very strong magnetic field.

The greater the current in the coil, the stronger the magnetic field generated. However, this method does not exist indefinitely, and since all the magnetic fields are aligned, increasing the current in the circuit causes very little increase in the field. This state is called saturation.

When the electric current is removed, the magnetic domains within the core lose their alignment and return to their previous random arrangement. But some alignments remain and the core remains a weak magnet. This condition is called hysteresis. The residual magnetic field is also called residual magnetism.

The figure below shows the magnetic field lines around an iron-core electromagnet.

Properties of electromagnets

• The electromagnetic magnetic field has imaginary field lines like a permanent magnet.
• Like a permanent magnet, electromagnets have north and south poles.
• Electromagnets cost less than permanent magnets.
• The electromagnet power can be adjusted according to your needs.
• Electromagnets require a lot of maintenance.
• They are not suitable for small spaces as they require a lot of copper couplers.
• There are some side effects that must be considered when designing electromagnets, such as: B. ohmic heat, inductive voltage spikes, Lorentz forces, and core losses.

I amThis video, you can learn more about electromagnetism or electromagnetic force.

Difference between permanent magnet and electromagnet

After a thorough introduction and discussion of the characteristics of each, we will describe the difference between a permanent magnet and an electromagnet. These differences are mentioned in the following cases.

The difference in the types of magnetization

The main difference between permanent magnet and electromagnet is the way they are magnetized. The permanent magnet is permanently magnetized, but the electromagnet is temporarily magnetized.

The difference in materials

Another difference between permanent magnet and electromagnet is in their materials. Permanent magnets are usually made of hard materials, but the material used in the electromagnet is soft.

The difference in the positioning of the poles

The position of the poles is a difference between permanent magnet and electromagnet. With a permanent magnet, the poles are fixed and do not change. But with the electromagnet, the poles can change.

The difference in strengths

There is a difference between permanent magnet and electromagnet in strengths. The strength of the magnetic field in a permanent magnet is constant, but the strength of the electromagnetic magnetic field is proportional to the needs of the user.