Alignment of Domains in Magnetized and Un-magnetized Iron

1. Alignment of Domains in Magnetized and Un-magnetized Iron Magnetic Fields 2

2. S N • Un-magnetized domains are aligned in various directions • Magnetized domains are aligned in a N –S direction

3. S S N N 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)

4. A permanent magnet can be destroyed by heating or vibration • Change in the kinetic energy of atoms, domains are misaligned

5. Magnetic Field • A magnetic field ( ) is the region surrounding a magnet in which magnetic forces exist • Two kinds of magnetic force, attractive and repulsive

6. Laws of Magnets • Like poles repel • Unlike poles attract

7. Magnetic Fields • 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

8. 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

9. Magnetic Flux Density • 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

10. 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

11. Earth’s Magnetic Field • 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)

12. Earth’s core-cross section 22° E of N in Alberta Magnetic north in the northern hemisphere South magnetic pole of the Earth’s magnetic field