RADT 142 - Week 10: Magnetism Study Guide

What is magnetism?

Charged particles in motion exhibit magnetism.

Ex.) Electrons-

What is magnetic domain?

Accumulation of many atomic magnets​.

Electrons/particles need to be in motion to exhibit magnetism

What is the nature of magnetism?

Magnetic materials are usually in a non-magnetized state where domains are in random arrangement

Random domains = No magnet

A _________is a small region within a material where the atoms all align with each other.

A magnetic domain is a small region within a material where the atoms all align with each other.

Domains align when a _____ is introduced.

Domains align when a magnetic field is introduced.

- Results in a magnetized material with a N to S orientation​

- Effectively one North pole and one South pole

What are the SI units of Tesla (T) & Gauss (G)?

1 G = 1x10^-4 T or 0.0004 T

Tesla - MRI

They do not equal one another

What are the 3 classifications of magnets?

1. Natural (found in nature)

- Earth is dipole: has 2 poles (N & S)

- Magnetite (Iodoestone or Iron Oxide) is natural ore that exhibits magnetism

2. Artificial Magnets (man made)

- Hardened steel or alloy

- Compass

3. Electromagnetics (temporary)

- Created by a current of e- and iron core

The earth is _______. But is it a weak one or a strong one?

The earth is a magnet but a weak one.

What is permeability (susceptibility)?

How easily a material can be magnetized

High permeability → easy to magnetize

Low permeability → hard to magnetize.

What is retentivity?

The ability of a material to hold magnetization.

What is the relationship between permeability and retentivity?

Inversely related

What are the four magnetic classifications of matter?

1. Ferromagnetic: Materials that can be magnetized, exhibit strong magnetic properties and are strongly attracted to a magnet​.

Ferromagnetic ability goes up, the strength of the magnet goes up. direct relationship

2. Paramagnetic: Materials that are only weakly attracted to a magnetic field and loosely influenced by a magnetic field.

3. Diamagnetic: Materials that are weakly repelled by a magnetic field, cannot be magnetized, and are not attracted to a magnet.​

Most elements in periodic table are diamagnetic like silver and gold

Silver & gold are not attracted to magnets

4. Nonmagnetic: Materials that are unaffected by a magnetic field

What is the magnetic force field?

Lines of force (magnetic flux lines)​

Direction​:

N→S outside the magnet​

S→N inside the magnet​

Form a closed loop

What is magnetic field?

Field lines pass through both magnetic & non-magnetic materials​.

concentrated by magnetic materials

unaffected by non-magnetic materials

**Blue highlighted represents the green line in the image**

What is the Law of Magnetism?

Every magnet has two poles. Designated N & S.

What is magnetic law #2?

Like poles repel, unlike poles attract.

Attraction: When opposite magnetic poles are brought near each other — North (N) → South (S) — they pull together.

Repulsion: When like poles are brought near each other — North (N) → North (N) or South (S) → South (S) — they push apart.

What determines the strength of magnetism?

The number of field lines per unit area.

More lines means it's a stronger field closer to the source.

Less lines means weaker field further from the source.

How do you create a magnet?

By stroking an iron bar repeatedly with a magnet.

Iron has high permeability and can easily turn into a magnet. It also has low retentivity and loses its magnetism quickly.

permeability & retentivity relationship - inversely proportional