Magnetic Fields 2

Un-magnetized domains are aligned in various directions

Magnetized domains are aligned in a N –S direction

N S

If a bar magnet is broken, each piece has a N and S pole

A given pole cannot be separated from the other pole (there are no monopolar materials)

SN N S N S

A permanent magnet can be destroyed by heating or vibration

Change in the kinetic energy of atoms, domains are misaligned

A magnetic field ( ) is the region surrounding a magnet in which magnetic forces exist

Two kinds of magnetic force, attractive and repulsive

BB

Like poles repel

Unlike poles attract

Magnetic fields are vectors, have magnitude and direction

The direction of a magnetic field ( ) is defined as the same direction of the magnetic force exerted onto the north pole of a compass

B

The direction in which the N-pole of a compass points indicates the direction of magnetic field.

Line of force - the path taken by the N-pole of a compass when free to move in a magnetic field

The number of lines of force through a region or space is called magnetic flux density

The density is proportional to magnetic field strength

A – higher density of field lines, greater B, greater Fm

B – lower density of field lines, lesser B, lesser Fm

Greatest density of field lines is near the poles of a magnet

A

B

Magnetic lines of force are continuous

The direction of a magnetic field line outside a magnet is N to S and inside is from S to N

The Earth’s magnetic field is similar to a bar magnet

The field is the result of the fluid motion of iron within the earth’s core (read text for new theories)

22° E of N in Alberta

Magnetic north in the northern hemisphere

South magnetic pole of the Earth’s magnetic field