Magnetism

Magnetism is a force that acts at a distance and is caused by a magnetic field. This field is invisible but can be detected by its effect on magnetic materials and moving electric charges.

Magnetism is closely related to electricity - they are two aspects of the same fundamental force called electromagnetism.

A magnetic field is a region around a magnetic material or a moving electric charge where the force of magnetism can be detected.

Magnetic field lines are used to visualize the magnetic field. They always form closed loops, emerging from the north pole and entering the south pole of a magnet.

The strength of a magnetic field is measured in tesla (T) or gauss (G), where 1 T = 10,000 G.

Materials can be classified based on their response to magnetic fields:

• Ferromagnetic: Strongly attracted to magnets (e.g., iron, nickel, cobalt)
• Paramagnetic: Weakly attracted to magnets (e.g., aluminum, platinum)
• Diamagnetic: Weakly repelled by magnets (e.g., copper, silver, gold)

Ferromagnetic materials can be magnetized to create permanent magnets.

Electromagnetism is the relationship between electricity and magnetism. There are several key principles:

1. Moving charges create magnetic fields

When electric charges move (creating a current), they generate a magnetic field around them. This is the principle behind electromagnets.

2. Changing magnetic fields induce electric currents

When a conductor experiences a changing magnetic field, an electric current is induced in the conductor. This is called electromagnetic induction and is the principle behind generators and transformers.

3. Magnetic force on moving charges

A moving charge in a magnetic field experiences a force perpendicular to both its direction of motion and the magnetic field. This force is given by:

F = qvB sin θ

Where:

• F is the force in newtons (N)
• q is the charge in coulombs (C)
• v is the velocity in meters per second (m/s)
• B is the magnetic field strength in tesla (T)
• θ is the angle between the velocity and magnetic field

Magnetism has numerous applications in our daily lives:

• Electric motors: Convert electrical energy to mechanical energy using magnetic forces
• Generators: Convert mechanical energy to electrical energy using electromagnetic induction
• Transformers: Transfer electrical energy between circuits using electromagnetic induction
• Magnetic storage: Store data on magnetic materials (hard drives, magnetic tapes)
• MRI machines: Use strong magnetic fields to create detailed images of the body
• Maglev trains: Use magnetic levitation to move without touching the ground