Magnetism: Definition, History, and Applications

Magnetism

Definition and History

• Magnetism is a physical phenomenon that arises from the interaction between magnetic fields and moving charges or changing electric fields.
• The ancient Greeks discovered magnetism in the naturally magnetized iron ore lodestone.
• William Gilbert, an English physician, coined the term "magnetism" in 1600 and published the first comprehensive treatise on the subject.

Magnetic Fields

• A magnetic field is a region around a magnet or electrical current where the magnetic force can be detected.
• It is a vector field that has both magnitude and direction.
• Magnetic fields are created by:
  • Permanent magnets
  • Electric currents (e.g., solenoids, coils)
  • Changing electric fields

Magnetic Force

• The magnetic force is a force that arises from the interaction between magnetic fields and moving charges or changing electric fields.
• It is a vector force that acts perpendicular to the direction of motion and the magnetic field.
• The magnetic force is given by the Lorentz force equation:

F = q(E + v x B)

• Where F is the force, q is the charge, E is the electric field, v is the velocity, and B is the magnetic field.

Types of Magnetism

• Ferromagnetism: Permanent magnets, such as iron, nickel, and cobalt, exhibit strong magnetic fields.
• Paramagnetism: Materials, such as aluminum and oxygen, are weakly attracted to magnetic fields.
• Diamagnetism: Materials, such as copper and silver, are weakly repelled by magnetic fields.
• Electromagnets: Coils of wire wrapped around a core, such as iron, can be magnetized by an electric current.

Applications of Magnetism

• Electric motors: Convert electrical energy into mechanical energy using magnetic fields.
• Generators: Convert mechanical energy into electrical energy using magnetic fields.
• Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves to produce images of the body.
• Magnetic storage: Uses magnetic fields to store data on devices such as hard drives and magnetic stripes.