RADT 142 Unit 10 - Magnetism

Magnetism

Is exhibited by charged particles in motion

Magnetic domain

accumulation of many atomic magnets; a small region where the atoms all align with each other

Domains align when ________________________________________.

A magnetic field is introduced.

- Results in magnetized material with a N — S orientation

- Effectively one North Pole and one South Pole

T

Tesla

G

Gauss

T to G conversion?

1 G = 0.0004 T

Classification of Magnets

1. Natural

2. Artificial

3. Electromagnets

Natural magnet

Found in nature.

Ex. Magnetite, lodestone, iron oxide

What is earth?

a dipole; a WEAK magnet

Artificial magnet

Man made.

Ex. Hardened steel, alloy, compass

Electromagnets

Temporary. Made by a current of e- and iron core

Permeability

AKA susceptibility; ease with which a material can be magnetized

Retentivity

the ability of a material to hold magnetization

What is the relationship between permeability and retentivity?

inversely related

Ferromagnetic

Materials that can be (1) strongly magnetized, (2) exhibit strong magnetic properties, and (3) are strongly attracted to a magnet

Paramagnetic

Materials that are only weakly attracted to a magnetic field and loosely influenced by a magnetic field

Diamagnetic

Materials that are (1) weakly repelled by a magnetic field, (2) cannot be magnetized, and (3) are not attracted to a magnet

Nonmagnetic

Materials that are unaffected by a magnetic field

Magnetic flux lines

Parallel lines of force that always go from N —> S outside the magnet, and S —> N inside the magnet; together form a closed loop

Field lines pass through________________________________.

Both magnetic AND nonmagnetic materials

Law of Magnetism

Every magnet has two poles: N & S

Magnetic Law #2

Like poles repel, unlike poles attract

Strength of magnetism is determined by _________________________.

# of field lines per unit area; more lines, stronger & closer to the source (similar to inverse square law)

How to create a magnet

Stroke iron bar repeatedly against magnet

What are the magnetic properties of iron?

High permeability and low retentivity; becomes magnetized quickly, loses magnetization easily