Magnetism and Its Properties

Magnetism

• Magnetism is a fundamental property of matter that attracts iron.
• It is caused by an electric charge spinning on its own axis, creating a magnetic field.
• Magnetic fields are always closed loops, with a north and south pole (bipolar or dipolar).

Types of Magnetic Materials

• Ferromagnetic: Strongly magnetized, examples are iron, nickel, and cobalt.
• Paramagnetic: Weakly attracted to magnetic fields, example is gadolinium.
• Diamagnetic: Weakly repelled by magnetic fields, examples are water and plastic.
• Magnetic Susceptibility: The degree to which a material can be magnetized.
• Magnetic Permeability: The ability of a material to attract lines of magnetic field intensity.

Magnetic Laws

• Like magnetic poles repel, unlike magnetic poles attract.
• The strength of the magnetic force is proportional to the product of the pole strengths divided by the square of the distance between them (Gauss's Law).
• There is no smallest unit of magnetism.

Naturally Occurring Magnets

• Earth
• Lodestones

Artificially Induced Permanent Magnets

• Horseshoe magnet
• Bar magnet

Electromagnets

• Consist of a wire wrapped around an iron core.
• A magnetic field is created when electric current is conducted through the wire.

Nonmagnetic Materials

• Unaffected by a magnetic field.
• Examples are wood and glass.

Electromagnetism

• Electricity and magnetism are different facets of the same force, the electromagnetic force.
• Key figures:
  • Luigi Galvani
  • Alessandro Volta (invented the Voltaic pile)
  • Hans Oersted (discovered that electricity can induce a magnetic field)
• The direction of the magnetic field around a wire can be determined using the right-hand rule.

Solenoid

• A coil of wire.

Induced Current

• The magnitude of the induced current depends on:
  • Strength of the magnetic field
  • Velocity of the magnetic field
  • Angle of the conductor to the magnetic field
  • Number of turns in the conductor

Electric Generator

• Converts mechanical energy into electrical energy (mechanical motion produces electric current).

Electric Motor

• Electric current produces mechanical motion.

Induction Motor

• Used in x-ray tubes to power the rotating anode.