Magnetism (RADS 354)

Magnetism

the ability of certain materials to attract iron, cobalt, or nickel any material that attracts these is a magnet

Unit of magnetism

Tesla (T) and Gauss (G)

- 1 T=10000 G

3 types of magnets

Natural (Lodestones), Artifical Perminant, and Electromagnet

Example of Natural Magnets (Lodestones)

the earth and iron oxide

Artificial Permanent Magnets

hard steel in the shape of a horseshoe or a bar that has been artificially magnetized by being rubbed with a magnet

ex. alnico an alloy made of aluminum, nickel, and cobalt

Electromagnet

a temporary magnet of iron produced by means of an electrical current

Magnetic Poles

there will be two areas of attraction on a bar magnet the two ends of a magnet where the magnetic forces are strongest

-one is a north and the other is south

The magnetic field is often referred to as...

dipole or bipole

When it comes to magnetism, electrons with pairs will..

neutralize the magnetic field meaning they are no longer magnetic

Magnetic domains

dipoles spin predominantly in one direction and this is an accumulation of such dipoles resulting in the formation of magnetic poles

When it comes to magnetism, atoms with an odd number of electrons in any shell will always have a...

small magnetic field

A magnetic element can exist either in...

non-magnetized or magnetized state

With a Non-Magnetized piece of iron the atoms are...

disorderly arranged (not organized)

With Magnetic Iron the magnetic domains will be...

aligned in an orderly fashion forming the poles of a magnet (organized)

Magnetic Field

the zone of influence that is created by any charges particle in motion

-traveling in the same direction they repel and if traveling in opposite directions they will attract)

Unit of magnetic flux

Weber (Wb)

- 1 Wb = 10^8 lines of flux per sq cm

Strength of magnetic field

Proportional to the number of lines per square centimeter

Characteristics of Lines of Force

1. Lines of force are directed from the north pole to the south pole of magnet

2. Lines of force seem to repel each other when they are traveling in the same direction, and attract each other when they are traveling in opposite directions.

3. The lines of force are distorted by magnetic materials (iron, cobalt, nickel), but not affected by nonmagnetic materials (glass or plastic)

3 Fundamental laws of Magnetism

Magnetic poles, Repulsion-attraction, and Inverse Square Law.

Magnetic Poles (Law of Magnetism)

every magnet has two poles, a north and south pole

Repulsion and Attraction (Law of Magnetism)

Like poles repel and unlike poles attract

Inverse Square Law of Magnetism (Law of Magnetism)

The force between 2 magnetic fields is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them

Magnetic Induction (Magnetization)

A piece of non-magnetized iron brought near one pole of a magnet, the iron end nearest the pole assumed the opposite polarity and the iron is now magnetized

- and when the iron is removed from the magnetic field, its domains again become jumbled, losing its magnetism

Magnetic Permeability

the ease at which a material can be magnetized

Magnetic Retentivity

the ability of a magnet to stay magnetized

Soft iron has _______ permeability and ________ retentivity.

high; low (easy to become a magnet, but once away from the magnet it loses its magnetism)

Hard steel has ___ permeability and ___ retentivity

low; high (hard to become magnetized, but once it is it stays a magnet)

Non-magnetic materials

materials not attracted to magnets because they are not susceptible to magnetic induction

ex. wood, glass, plastic

Diamagnetic materials

Materials that are weakly repelled by either magnetic pole (magnetic fields), cannot be artificially magnetized and are not attracted to a magnet

ex. water, plastic, beryllium, and lead

ferromagnetic materials

strongly attracted to magnets because of high permeability

ex. iron, cobalt, nickel

Paramagnetic materials

between ferromagnetic and nonmagnetic are feebly attracted to magnets and has extremely low magnetic permeability

ex. platinum & aluminum, Gadolinium

Detection of Magnetism is done by

Magnetic Compass

Magnetic Compass always points

to geographic north