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) S N 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

 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

 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 F m  B – lower density of field lines, lesser B, lesser F m  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