Concept of magnetism and matter

The Earth behaves as a magnet pointing approximately from the geographic south to the north. The magnetic properties of a molecule depend upon the connection between the magnetic moments of atoms and electrons. The magnetic moment of an atom is thousands of times smaller than the magnetic moment of electrons. 

Magnetism is a property by which the phenomenon of attraction and repulsion is produced by a moving electric charge. We know the electric charge is surrounded by electric field lines the same as a magnet is surrounded by a magnetic field. Magnet exerts a force that comes as a result of moving electric charge. There are some types of magnetism that are described according to their bulk liability.

What is magnetism?

A magnet has the property to repel or attract other substances, which is referred to as magnetism. When two bar magnets are positioned close to one another, the same poles will repel each other; however, the opposite poles tend to attract. The primary reason behind this behaviour of the magnet is the imaginary magnetic line that continuously revolves around. Similar to the electrostatic force and the gravitational force, magnetism is also a type of interaction from a distance.

Matter and magnetism

Magnetism occurs due to magnetic fields surrounding matter. This leads to the formation of magnetic materials that react in a certain way.

Types of magnets

There are generally three types of magnets:

• Permanent magnet

• Electromagnets

• Temporary magnets

Permanent magnet 

As the name suggests, permanent magnets are those magnets that do not lose their magnetic properties in a lifetime once they are completely magnetised. However, permanent magnets can be demagnetised if placed at extremely high temperatures or by stroking two magnets inappropriately. Generally, there are four major types of permanent magnets. These are:

• Ferrite or ceramic 

• Samarium Cobalt (SmCo)

• Alnico

• Neodymium Iron Boron (NIB)

Electromagnets

Electromagnets are wire coils that have a ferromagnetic core. In case the electric current passes through the electromagnets, they start to react like bar magnets. Electromagnets do not have permanent magnet pull since these are highly dependent on external factors. 

Temporary magnet 

These magnets are magnetised only when the magnetic field is present. However, these lose their magnetic property once it is removed. Some examples of temporary magnets are paper clips and iron nails.

Properties of magnets

• Attractive property: It tends to attract substances such as iron, nickel, and steel.

• Directive property: Materials having magnetic property align in a north-south direction.

• Repulsive property: Like magnetic poles repel and unlike ones attract each other.

• Two poles: Magnetic poles cannot be isolated, which signifies that they always exist in pairs. 

• Magnetic field lines: It is the curved lines that tell the direction of a magnetic field.

• Magnetic induction: A magnet tends to induce some magnetic property to a substance that is placed nearby. This process is called magnetic induction.

Magnetic dipole

The setup of two equal and opposite magnetic poles which are separated by some distance is known as a magnetic dipole. Magnetic dipole moment can be calculated as the product of its pole strength (qm) and magnetic length (2l).

m=qm2l

What is a magnetic field? 

Similar to the gravitational field, the magnetic field cannot be touched or seen. The pull of the Earth’s gravitational field can only be felt on the objects around us and even on ourselves. The existence of magnetic fields can be determined by their effects on different objects such as pieces of metal, copper coil carrying the electric current, and lodestone, a naturally magnetic rock. Let us understand this via an example.

Suppose you sprinkle tiny iron pieces or filings on a white paper along with a magnet bar in between. Every time you tap on the paper, the iron filings will be aligned around the magnet bar. Some properties of the magnetic field lines are:

• The magnetic field lines do not have an intersection point.

• The magnets’ magnetic field lines build a continuous closed loop.

• The more the magnetic field lines, the stronger the magnitude will be.

Diamagnetism

These types of substances have a propensity to move from the stronger part to the weaker part of the external magnetic field. In other words, unlike magnets, they attract metal like iron, but it would repel a diamagnetic substance due to the absence of permanent dipoles. Some diamagnetism materials are bismuth, lead, water, copper, nitrogen (at STP), sodium chloride.

Paramagnetism

These substances are weakly magnetised when kept in an external magnetic field. They have a propensity to move from weaker magnetic fields to stronger magnetic fields. They get easily attracted to a magnet due to unpaired electrons. Some paramagnetic materials are aluminium, sodium, oxygen (at STP), calcium.

Ferromagnetism

Such magnets are strongly magnetised when they are kept in an external magnetic field. Like paramagnetic substances, they have a propensity to move from weaker magnetic fields to stronger magnetic fields. Ferromagnetism is found only in a few substances like iron, nickel, cobalt, and their alloys. 

Conclusion

Magnetic phenomena are universal in nature. The Earth behaves as a magnet pointing approximately from the geographic south to the north. The molecule property of any substance depends on the magnetic moment of the atom and electron. Materials can be classified based on their magnetic properties.