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