Magnetism

Magnetism is a branch of physics that deals with the properties and interactions of magnets. It explains how magnets exert force on each other and other materials. It also arises due to moving electric charges. At the atomic level, it mainly arises from the orbital motion and spin of electrons.

Properties of Magnetism

Attraction & Repulsion: In a magnet, like poles repel each other, and unlike poles attract. The attraction is stronger at the poles than in the middle of the magnet.
Poles Exist in Pairs: A magnet always has two poles: North and South. If a magnet is broken into two parts, each part becomes a new magnet with both poles.
Magnetic Field: A magnet creates a region of force around it called the magnetic field. This field can attract or repel other magnetic materials.
Direction: A freely suspended magnet always points in the north-south direction.

Force in Magnetic Poles

The force between two magnetic poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between them. This is known as Coulomb’s Law in Magnetism:

Mathematically:

formula

Where:

F - force between the poles

m₁ and m₂ - pole strengths
r - distance between the poles
μ₀ - permeability of free space

Earth’s Magnetism

Earth is a natural magnet. It behaves like a giant bar magnet. The magnetic north pole is actually a south magnetic pole, and vice versa; this can be proven because it attracts the north pole of a compass, and we know that unlike poles attract.

Magnetic declination: The angle between geographic and magnetic meridians.
Magnetic inclination: The angle between the Earth's magnetic field and the horizontal plane. It is also known as a dip.

The Earth’s magnetic field strength ≈ 3.5 × 10⁻⁵ T at the equator.

Types of Magnetic Materials -

Diamagnetic materials- These have a weak and temporary magnetic moment in the opposite direction of the applied magnetic field. Magnetic fields slightly repel them. These materials do not retain magnetism once the external field is removed and have no unpaired electrons. Examples: bismuth, copper, and silver
Paramagnetic materials - These have unpaired electrons that align with an external magnetic field, which makes them weakly attracted to it. However, this magnetism is not retained when the external field is removed. Examples: aluminium, platinum
Ferromagnetic materials - These show strong attraction toward magnetic fields and can become permanently magnetised. Their atoms have magnetic moments that align in the same direction, even when an external field is not present. This makes them ideal for permanent magnets—examples: iron, nickel, and cobalt. They exhibit hysteresis and can retain magnetisation strongly.

Applications

Transformers
Magnetic storage devices
Credit/debit cards
MRI machines
Maglev trains
Magnetic cranes
Speakers & microphones
Compass
Magnetic sensors

Summing Up

Magnetism is the study of magnetic forces and interactions created by moving electric charges. Magnets show attraction and repulsion, always have north and south poles, and create magnetic fields. Earth itself acts like a giant magnet. According to Coulomb’s law, the magnetic force depends on pole strength and distance. Magnetic materials are classified as diamagnetic, paramagnetic, or ferromagnetic, based on magnetic fields. Magnetism is widely used in devices like transformers, MRI machines, maglev trains, and storage media.