Poles of Magnets

Introduction

Every matter in the universe is composed of tiny particles called molecules. They attract each other with some attractive force. There exists an intermolecular force of attraction between molecules. Likewise, the electromagnetic force is the force of attraction or repulsion between charged particles. Magnetic force is part of the electromagnetic force.

What are magnets?

Magnets are materials that are having a magnetic field around it. Some materials get magnetized by giving magnetic fields. This is known as magnetism. All magnets cannot have the same material. The materials used for magnets are of three types such as diamagnetic materials, paramagnetic materials, and ferromagnetic materials. Permanent magnets are materials having high magnetic properties that hold their magnetism for a very long period. Ex: iron, nickel, cobalt, etc. Temporary magnets are materials that have low magnetic properties that get magnetized in the presence of a magnetic field and hold for a short period. Ex: Soft iron or steel. Electromagnets are the unmagnetized material that gets magnetized only when it is placed in the magnetic field.

Types of magnets

The magnets are of three types such as Permanent magnets, Temporary magnets and electromagnets.

Permanent magnets

• These magnets are materials having high magnetic properties that hold their magnetism for a very long period. Ex: iron, nickel, cobalt, etc.

• Permanent magnets are magnets that have long-lasting magnetism such as a natural magnet (magnetite), or man-made magnets made from nickel, or cobalt alloy.

• In permanent magnetic materials, the magnetic field is created by the material itself. The magnetic field of the permanent magnet is calculated by adding nuclear spin, electron spin, and orbits of the electrons.

• There are many types of permanent magnets according to their properties and compositions such as Ceramic, Alnico, Neodymium Iron Boron, Samarium Cobalt, Injection-molded, and flexible.

Electromagnets

• Electromagnets are the unmagnetized material that gets magnetized only when it is placed in the magnetic field. The basic principle of electromagnets is electromagnetism.

• By giving current to the conductor a magnetic field is produced. This process is called electromagnetism. The basic concept is electromagnetic induction. If a current is applied to the carrying conductor and is placed in a magnetic field then there is an induced emf which induces a current.

• Electromagnets are temporary magnets that get magnetized by passing a current through the coil of wire. If there is a current flowing through the coil, the electric field induces a magnetic field in the center of the coil. It becomes powerful by introducing an iron rod through the coil.

• Once after current passing through the coil is stopped, then suddenly the iron rod loses its magnetic power.

Temporary magnets

The magnets that are made by humans are temporary magnets. When the magnetic materials are placed in a magnetic field then it gets magnetised. When the applied magnetic field is removed it loses its magnetism. They are not having the ability to sustain its magnetism like a permanent magnet. This is the reason for the name of the magnet. Some of the examples are iron, paper clip, iron nail etc.

Magnetic poles

Generally, magnets have two poles. One is the south pole and another one is the north pole. By hanging the magnets using a thread it lies in the earth’s magnetic field direction by which the poles are identified. Magnetic lines of force act between two poles starting from the north pole and ending at the south pole of the magnet. Magnetic fields are stronger at the poles and weaker at the intermediate. The region around which the magnets have magnetism is known as the magnetic field. If the bar magnet is suspended freely the magnet’s north and south pole lie in the same direction of the magnet and align themselves to the direction of the north pole and south pole of the earth.

Pole Strength

The strength with which the materials get attracted to the magnet is referred to as the pole strength of the magnet (m). Magnetic moment (M) is calculated by multiplying the pole strength of the magnet and its length (l). Unit of pole strength is A.m.

$$\mathrm{Pole\: strength=\frac{Magnetic\: moment }{length\: of\: magnet}}$$

$$\mathrm{m=\frac{M}{l}}$$

Magnetic lines of force

The magnetic field represents the magnetic impact of the materials and charges. The magnetic field is a vector field that best describes the region of magnetism. The visual representation of the magnetic field is done by the magnetic field lines.

Properties of magnetic lines

• Magnetic field lines do not cross each other.

• As magnetic lines originate from the north pole and end at the south pole, the field is stronger at the poles.

• They are always in a closed loop.

• The magnetic field strength is calculated by the magnetic field density.

Conclusion

Magnets have two poles such as north and south poles and they cannot be interchanged. When it is made to hang it shows the direction of the poles of the earth. There is a magnetic line of force which starts from the pole north to south. Poles have strong magnetic fields.

FAQs

1. Why do the same poles repel each other and different poles attract each other?

Magnetic lines drawn from the north pole and complete at the south pole of the magnet. When two magnets with the same pole are brought together their magnetic lines are opposite to each other so they repel each other. If the different poles are brought together their magnetic lines are in the same direction so they attract each other.

2. What happens to the poles when the magnet gets broken?

If the magnets get broken accidentally or intensively the poles of the magnet do not change. Every broken piece has its own north and south poles.

3. What is the need for horseshoe-type magnets?

Horseshoe magnet is made in the shape of a horseshoe or U shape. According to the properties of magnets, the magnetic field is stronger at the poles than at the center. As the horseshoe magnet is in the U shape their two poles are in the same direction. And so their pole strength becomes very high. So horseshoe magnets are powerful magnets and are used to lift heavy objects.

4. What are the characteristics of electromagnets?

• Electromagnets run only on electricity.

• They are easily demagnetized by removing the current that passes through them.

• Material used for making an electromagnet is soft iron.

• By changing the current that flows through the circuit the magnetic field strength of the electromagnet is changed by changing the current that passes through it.

• Polarity of the electromagnet can be changed by changing the direction of current through it.

5. What is retentivity?

The ability of the material to retain its magnetism is called retentivity. The Retentivity of the permanent magnet is high. That is why they have permanent magnetism.