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Hysteresis

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Last updated date: 23rd May 2024
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What is Hysteresis?

Hysteresis happens in a system that involves a magnetic field. It is also the common property of ferromagnetic substances. In general, when the magnetization of ferromagnetic materials lags behind the magnetic field, this effect can be referred to as the hysteresis effect.

 

The terms “hysteresis” means ”lagging.”  The term, Hysteresis, is characterized as a lag of magnetization intensity (B) behind the intensity of the magnetic field (H).

 

All the ferromagnetic materials exhibit hysteresis phenomena. To understand the concept in a better way, let us take an instance where a ferromagnetic substance is kept inside a current-carrying coil. Due to the magnetic field, which is present, the substance gets magnetized. If we reverse the direction of the current flow, the substance gets demagnetized, and this process is called Hysteresis.

 

There are two types of Hysteresis, which can be given as,

  • Rate-dependent hysteresis

  • Rate-Independent hysteresis

 

Hysteresis Loop

The hysteresis loop indicates the relationship between the intensity of magnetization and the magnetizing field. This loop is generated by measuring the magnetic flux that is coming out from the ferromagnetic substance while changing the external magnetizing field.

 

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Pointing to the graph, if B is measured for different values of H and if we plot the results in graphic forms, the graph will indicate a hysteresis loop.

  • The intensity of the magnetism (B) increases when the magnetic field (H) is increased from 0 (zero).

  • With the increased magnetic field, there is an increase in the magnetism value and finally reaches point A which is known as a saturation point where B is constant.

  • With the decrease in the value of the magnetic field, there is a decrease in the magnetism value. But, at point B and H are equal to zero, material or substance retains a few amounts of magnetism, called residual or retentivity magnetism.

  • When there occurs a decrease in the magnetic field towards the negative side, there happens a decrease in magnetism. At point C, the substance is entirely demagnetized.

  • The force that is required to remove the retentivity of the material is called Coercive force (C).

  • The cycle is continued in the opposite direction, where the retentivity point is E, the saturation point is D, and the coercive force is F.

  • Due to the opposite and forward direction process, the cycle is complete, and this cycle is known as the hysteresis loop.

 

Advantages of Hysteresis Loop

A smaller region of loop hysteresis is a sign of less loss of Hysteresis. The hysteresis loop gives a substance with the importance of coercivity and retentivity. Therefore, selecting the way of the right material to make a permanent magnet is made simpler by the heart of machines.

 

Residual magnetism can be calculated by the B-H graph, therefore, it is simple to choose material for electromagnets.

 

Energy Loss Due to Hysteresis

The best example of knowing energy loss due to Hysteresis is a transformer, and as we know that during the magnetization and demagnetization process, the energy is required.

 

During the magnetization and demagnetisation cycle of magnetic substances, some energy will be spent. This spent energy appears in the form of heat, and this heat loss is known as hysteresis loss.

 

Energy loss per unit volume of the substance = Area of the hysteresis curve

 

In Transformers, the energy is lost continuously in the form of heat because of the continuous magnetization and demagnetisation process. Due to this, the energy loss efficiency of the transformer gets reduced.

 

To stop this energy loss, a soft iron core is used in the Transformers because the hysteresis loss or the energy loss in the case of soft iron is much smaller than other materials.

 

Difference between Soft and Hard Magnetic Materials

Soft Magnet

Hard Magnet

Magnetization and demagnetization process is easy.

Magnetization and demagnetization process is difficult.

A soft magnet can be formed by heating and then cooling gradually.

A hard magnet can be formed by heating and then cooling suddenly.

The hysteresis loop area is small, and the retentivity and coercivity are also small.

The hysteresis loop area is large, whereas the retentivity and coercivity are also high.

These are temporary magnets.

These are permanent magnets.

Examples are Ferrites Garnet, Ferrous-nickel alloy.

Examples are tungsten, Steel, carbon steel, and chromium steel.

 

Soft Iron vs. Steel

  • Soft iron can magnetize and demagnetize easily compared to Steel

  • Retentivity of soft iron is more to that of the retentivity of Steel

  • The coercivity of steel is more compared to the coercivity of soft iron

  • Because of the small area, the energy loss in soft iron is less compared to the energy loss in steel

  • The area of the loop in case of soft iron is less than that of steel

  • Both I and χ are high in soft iron, whereas both are low in steel

  • Soft irons are used in electromagnetic tapes, transformers, tape recorders, and many more

  • Magnetic permeability is high in soft iron to that of steel


 How to Study for Hysteresis

  • Go through Hysteresis – Definition and Advantages of Hysteresis Loop on Vedantu

  • Read the content of the page thoroughly

  • Go through each and every part and especially over the parts that need re - reading

  • Highlight all the key areas of the chapter

  • Do not skip any section on the page

  • Write down everything in your own language someplace to understand it better

  • Revise from the page before any test on the chapter


How Vedantu Educates Students  on Hysteresis?

Yes, vedantu has ample study material that’s needed for the students to know about. It has Hysteresis – Definition and Advantages of Hysteresis Loop on its online tutoring platform for the students to read from. All students who need to get their basics on the chapter right can read from here. Vedantu only has relevant study material on its portal and so the students can read from it without getting anxious.

FAQs on Hysteresis

1. Explain Magnetization and Demagnetization?

The method of developing the magnetic properties inside a magnetic substance is called magnetization; any of the magnetic substances can be magnetized using an electric current or by touching with a strong magnet.


In simple words, if we put any magnetic substance in the external magnetizing field, then the corresponding material gets magnetized, and if we reverse the direction of the external magnetizing field, then the material or substance gets demagnetized.


If ferromagnetic materials are located inside a current-carrying coil, the magnetizing field H is caused by the current forces, a few or all the atomic magnetic dipoles present in the material to align with the external magnetizing field. In this way, the material gets magnetized.

2. Explain Retentivity and Coercivity?

If a ferromagnetic material gets magnetized by applying the external magnetizing field, if we remove the external magnetizing field after magnetization, the material will not relax back to its zero magnetization position.


Retentivity: The magnetization amount available when the external magnetizing field is removed is called retentivity.


A material is able to retain some amount of magnetic property while an external magnetizing field is removed.


The value of B at point b present in the hysteresis loop.


Coercivity: The reverse (-ve H) external magnetizing field amount required to completely demagnetize the substance is called coercivity of substance.


The value of H at point c present in the hysteresis loop.

3. Are there any merits of the hysteresis loop?

Yes, the hysteresis loop makes permanent magnets more prominent. The smaller the hysteresis loop area of a magnetic material, the less is the hysteresis loss. The hysteresis loop area for silicon steel is quite small and so, silicon steel is used in the manufacturing of transformer cores.   They are also used across other industries. The descriptions for these have been provided on Vedantu’s online tutoring portal.All the stuff included here is free of cost for the students. They can click on Hysteresis – Definition and Advantages of Hysteresis Loop  and then get to know the rest of the details. This page is quite informative for all those who read it. A hysteresis loop gives a substance with the importance of coercivity and retentivity.  This assists in making permanent magnets in an easier manner.

4. How are soft and hard magnets different from each other?

Soft and hard magnets differ in terms of their characteristics. A soft magnet can be formed by heating and then cooling gradually whereas a hard magnet is formed by heating and cooling suddenly.  Soft magnets are temporary magnets but the hard ones are permanent magnets.  Examples of soft magnets are ferrite garnet, ferrous nickel alloy and some examples of hard magnets are tungsten, steel, carbon, steel and chromium steel.  Students will understand this in a better manner after having gone through this page on Vedantu-  Hysteresis – Definition and Advantages of Hysteresis Loop. 

5. How are soft iron and steel different?

Both soft iron and steel are different in terms of their composition. They have different properties . Students can find out more if they read from Hysteresis – Definition and Advantages of Hysteresis Loop.  This page has all the relevant bits of information that are needed by the students to know.  Soft iron can magnetize and demagnetize easily compared to steel, retentivity of soft iron is more than the retentivity of steel, the coercivity of steel is more than the coercivity of soft iron. 

6. Is Hysteresis a complex chapter for students to understand?

Students can read from Hysteresis – Definition and Advantages of Hysteresis Loop online and then understand the matter. Hysteresis is an important chapter and will also come for all future engineering related entrance exams.  They can go through this page entirely and then make notes on the same. Reading each and every line will assist them in understanding the topics in a better manner. They can also read from the page prior to an exam so as to score well in all tests. Creating notes helps students understand the topic in a better manner as they retain those concepts for a longer period of time and also write well in the exams.All questions that come from the chapter can be dealt with if the notes have been made and include every bit of information.

7. How can students know about the hysteresis loop?

Students can read about the hysteresis loop online by referring to Hysteresis – Definition and Advantages of Hysteresis Loop on Vedantu’s platform. In a hysteresis loop, each and every molecule of a material happens to be a magnet with a north and a south pole. All molecules must align themselves in the same direction to acquire the maximum flux density. Once all the molecules are aligned, flux density reaches its maximum value, causing the core to become quite saturated. This page has all explanations related to the chapter and is  a blessing for all those who need explanation in simple terms. It is the ideal guidebook for students to read from as it has explained all the vital topics and sub-topics quite well. They can refer to it in an offline mode as well if they download it in a PDF form.