Magnets - Permanent Magnets and Electromagnets

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Magnets Introduction:

Magnets are a piece of a substance which are having the property of attracting other substances like iron , steel, nickel, cobalt etc  and rest in the north south direction, when suspended freely. They are of two types named natural magnet and artificial magnet (Man-made) . Bar magnet , U-shaped magnet are some of the examples of Man made magnet . 

Various properties of magnetic materials for example;  permeability, retentivity, coercivity ,  susceptibility, energy loss etc. help in selection of proper for a specific purpose. Curve between B and H i. e. Hysteresis loop of various materials readily pin point the right material for the right purpose :

What are permanent magnets? 

Permanent Magnets  are the substances which retain their Ferromagnetic properties for a long time at room temperature. 

Permanent magnets

Materials for making permanent Magnets should have :

i)  High permeability  ii) And High coercivity iii)  High retenivity.

Steel is a common material used to make permanent magnet.  It has high retentivity i. e.,  residual magnetism. It has very high coercivity . Although area of Hysteresis loop for steel is large. Yet it is of no importance because a permanent magnet is supposed to retain the magnetism. It is not required to undergo magnetisation and demagnetisation. As far as retentivity is concerned, it is smaller than that of soft iron. Coercivity of soft iron is very less which makes soft iron unfit for becoming permanent magnet. 

Many alloys are also used to make permanent Magnets :

i) Cobalt steel : it contains cobalt, carbon, iron and tungsten. 

ii)  Alnico : It contains aluminum, copper,  nickel and iron. It is brittle. 

iii)  Ticonal: It contains Tin, cobalt ,aluminum and Nickel. 

Permanent Magnets  are easy to made. They can be made by rubbing a Ferromagnetic material say iron bar with a magnet in a particular fashion. These can also be made, when placing hard Ferromagnetic bar in a current carrying solenoid. The magnetic field of solenoid,  magnetises the Ferromagnetic material.

Related Topics :

👉 : magnets - Types and properties complete information

visit : What are magnetic substances

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What are Electromagnets? 

A Ferromagnetic material placed inside a current carrying solenoid acts as an electromagnet. When a soft iron rod is placed inside a current carrying solenoid, it behaves as an electromagnet. 

Materials for making electromagnets should have :

i)  High permeability ii) Low Coercivity iii) And Low retentivity. 

Soft iron is a Ferromagnetic substance and has high permeability and low retentivity .These properties of soft iron makes it suitable for making an electromagnet. 

When current in a solenoid is switched on That's the current is allowed to pass , the soft iron rod placed inside it is magnetised at once. on the other hand,  it ceases to be a magnet , as soon as the current in the solenoid is switched off. 

Cores of generators. transformers and motors are magenetised and demagnetised number of times, when AC flow through them. Hence,  the materials having narrow hysteresis loops should be used to prepare these cores. 

Mumetal , an alloy of Ni, Fe, Cu and Cr including iron and silicon are used to form cores of transformer. 

Note:

Normal ratio of nickel, iron, copper and chromium in mumetal is 76% , 17% , 4% , and 3% respectively. 

Normal ratio of nickel, iron,cobalt , aluminum and copper in Alnico is 54% , 18%, 12% , 10% and 6% respectively.

Factors deciding the strength of an Electromagnet: 

i) Nature of material :

Soft iron is suited best for making of an electromagnet . Material of an electromagnet should have thin and long hysteresis loop . The material should magnetise quickly, when placed in the magnetising field. They should have low retentivity. They should also have a high permeability. Iron, silicon and mumetal are also used to make electromagnet.

ii)  Temperature :

Magnetism is lost at high temperatures. Therefore, to retain the magnetism in a given substance, its temperate should be low. 

iii)  Number of turns per unit length of a solenoid :

Magnetising field of solenoid depends upon the number of turns. Higher the number of turns, higher is the magnetising field. High field is required for strong electromagnets. 

iv)  Electric current: 

To magnetise a substance strongly, placed in a solenoid, strong magnetic field is needed. Magnetic field in a solenoid depends on the strength of electric current. If current in a solenoid is large, substance in the solenoid is strongly magnetised. And If current in a solenoid is small, substance in the solenoid is weakly magnetised. 

Uses :

Electromagnets are usually found in lifting magnets, relays, controllers, circuit breakers, electric valves, electric bells, loudspeakers, motor breaks etc. 

Conclusion:

As you already know that this article has discussed about Permanent magnet and Electromagnets. The concept of  magnet has much importance in scientific world. Like for example,  concept of Gravity is having a big relation with it. 

However, the article also discussed about the methods required to make magnet. The article provide you a brief but complete information. The factors deciding the strength of an Electromagnet its uses is also described in parts, which would make it more easy for you to understand . 

In conclusion I hope now the concept of permanent Magnets  and Electromagnet is now clear to you. please share this article on social media and other sources. so that we can reach out to more audience. For more information about different physics concepts visit "physics guide ". Thank you for your visit. Good luck!