Magnetic Fields - (Physics 3)

Poles

Two ends of a magnet where the magnetic fields are stronger

North Pole

Magnetic field lines enter the planet vertically downward

South Pole

Magnetic field lines point vertically and emerge from the surface

Compass

Magnetized needle that swings freely on a pivot

Maglev Magnetic fields

Used in maglev trains to achieve frictionless suspension and propulsion by using strong magnetic fields to levitate the train above the tracks and then pull or push it forward

Likeness between magnetic force between two magnets

The electric force between charged objects in that unlike poles of two magnets attract one another and like poles repel one another

Alike poles

Repel each other

Different poles

Attract one another

Ferromagnetic

Materials where the magnetic fields produced by the the electron spins do not cancel completely

Magnetic poles

Only occur in pairs

Magnetic domains

A region composed of a group of atoms whose spins are aligned in the same direction

Domain size range

From about 10^-4 to 10^-1

Classification of a magnetic piece of a material

Magnetically hard or soft

Soft magnetic material

Easily magnetized but also tend to lose their magnetism quickly

Hard magnetic materials

Difficult to magnetize, but once they are magnetized, they tend to retain their magnetism

Removing the external field from soft magnetic materials

The random motion of particles in the material changes the orientation of the domains and the material returns to an unmagnetized state

Removing the external field from hard magnetic materials

Domain alignment persists, the result is a permanent magnet

Magnetic field

A region in which a magnetic force can be detected

Magnetic flux (Φ_M)

Magnetic field strength to define a quantity

Defined as the number of field lines that cross a certain area at right angles to that area

SI unit for magnetic flux (Φ_M)

Webber (Wb)

Magnetic flux equation

(Φ_M) = AB(cosθ)

Magnetic declination

The difference between true north, which is defined by the axis of rotation of Earth, and north indicated by a compass varies from point to point on Earth

Convection currents

Create magnetic fields, such as in Earth’s core, where molten iron flows and generates the planet's magnetic field