Introduction to Magnetism

Introduction to Magnetism

• Magnetism is a fundamental physical phenomenon related to the force exerted by magnets
• Magnets have north and south poles, which attract or repel each other
• The force between magnets originates from moving electric charges (electrons)
• Magnetic fields are invisible but can be visualized using magnetic field lines

Properties of Magnets

• Magnets attract ferromagnetic materials (like iron, nickel, and cobalt)
• Magnetic force is strongest at the poles of a magnet
• Like magnetic poles repel each other, while opposite poles attract
• A freely suspended magnet will align itself with the Earth's magnetic field, with its north pole pointing roughly towards the geographic North Pole
• Magnets can lose their magnetism over time through various means

Types of Magnets

• Permanent magnets retain their magnetism, even after a magnetic field is removed
• Temporary magnets lose their magnetism when the external magnetic field is removed
• Electromagnets are temporary magnets created by passing an electric current through a coil of wire

Magnetic Fields

• A magnetic field is a region of space where a magnetic force is exerted
• Magnetic field lines emerge from the north pole and enter the south pole
• The density of magnetic field lines indicates the strength of the field
• The direction of the magnetic field at a point is the direction in which a north pole would point at that point

Earth's Magnetic Field

• The Earth has a natural magnetic field, created by electric currents in the Earth's core
• This field protects the Earth from harmful solar radiation
• The Earth's magnetic field is not uniform and can vary in strength and direction

Electromagnetism

• A moving electric charge generates a magnetic field
• An electric current flowing through a wire creates a circular magnetic field around the wire.
• The strength and direction of the magnetic field are dependent on the current and the geometry of the wire
• Electromagnets can be stronger than permanent magnets and their strength can be controlled

Magnetic Domains

• Ferromagnetic materials consist of many tiny magnetic regions called domains
• Within each domain, the electrons spin in the same direction.
• When an external magnetic field is applied it aligns the domains to create a stronger magnet
• When the external field is removed, some domains become misaligned potentially reducing/removing the induced magnetism

Applications of Magnetism

• Magnets are used in various applications including: motors, generators, compasses, hard drives, medical imaging (MRI), and data storage.
• Electromagnetic induction is fundamental to electrical generation and data storage
• Magnetic levitation trains are based on strong magnets that repel and levitate the train above the tracks