Magnetism Notes

Magnetism

Magnets

  • Magnets are materials, often consisting of iron, where component atoms are arranged in the same direction.
  • This arrangement causes the material to attract other iron-containing objects through an external magnetic field.
  • Objects with magnetic properties have north and south poles.
  • These poles can either attract or repel each other based on their orientation.
  • Earth acts as a giant magnet.

Magnetic vs. Non-Magnetic Materials

  • The difference between magnetic and non-magnetic materials is the order of their atoms.

Magnetic Facts

  • Magnets always have two poles (dipole).
  • It's currently impossible to have a magnetic monopole.
  • Breaking a magnet results in each new piece having a north and a south pole.
  • A compass needle is a tiny magnet.

Rule

  • Like poles repel each other.
  • Unlike poles attract each other.

Magnetic Force

  • Magnetic force is a noncontact force between moving electric charges.
  • Electricity causes magnetism.
  • Electrons moving around an atom behave like tiny bar magnets.
  • Attraction or repulsion between large bar magnets results from the combined motions of trillions of electrons.
  • The magnitude of magnetic force is determined by charge strength and speed of motion.

Magnetic Fields

  • Magnetic forces can be explained by magnetic fields, similar to electrostatic and gravitational forces.
  • Magnetic field is a vector quantity.
  • The direction of the magnetic field is the direction the north end of a compass needle points.
  • Magnetic field lines visualize a magnetic field.
    • They have no start or end; they are continuous loops.
    • Magnetic field lines never cross one another.
  • Stronger magnets have more field lines per unit area.

Magnetic Field Lines

  • Magnetic field lines are drawn away from the north pole and towards the south pole.

Electromagnetism

  • Mass produces a gravitational field, and charge produces an electric field.
  • Moving charge (current) produces a magnetic field.
  • Moving electrons create current; therefore, a potential difference must exist.

Electromagnetic Induction

  • Electromagnetic induction is a current produced due to voltage production.
  • Electromagnetic induction requires relative motion between a conductor and a magnetic field.
  • A conductor must "cut through" a magnetic field to produce a current, or a magnet must move through a loop of conducting material.
  • If a conductor moves in the direction of the magnetic field, no potential difference is generated.