Different Types of Fields

G-field: gravitational field created by mass
E-field: electric field caused by charges
B-field: magnetic field caused by moving charges

Why is the magnetic field called a "B-Field"?

“B” because James Clerk Maxwell named the fields as he studied them as “A” “B” …

A: Electromagnetic momentum at a point- which has been changed to vector potential
B: Magnetic induction (field)
C: Total electric current
D: Electric displacement
E: Electromotive force
F: Mechanical force
G: Velocity at a point
H: Magnetic force (intensity)

I have also found references to "B" coming from a description of the magnetic field which has the shape of a butterfly. Although this is nonsensical it is a poetic way to remember the connection.

Causes of magnetism:

In the illustration above, the domains are not lined up.
All the different directions will cancel each other out and it will not be a magnet.

 








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In the illustration above, the domains are lined up. The strength of each domain is added to its neighbor and the material becomes a magnet.

Movement of charge- electrons moving will created a magnetic field.
Alignment of electron spin creates magnetism- the spin of electrons will create a magnetic field. Most electrons in most materials will pair up with a partner that will be spinning oppositely. They will cancel out each other’s fields. However, in other materials the spins can line up and join forces and amplify each other’s magnetic fields giving you a magnet.

A domain is a region where all of the electrons spin in the same direction. If all domains line up you have a magnet.

Heating or hitting a magnet will kill it.

 

This page is under serious construction. Below are just a bunch of raw notes.

 

Ferromagnetic materials
Iron
Nickel
Cobalt

Earth’s Magnetic field
Caused by the rotation of the FeNi core.
The north end of a magnetic compass points N
The magnet in the core is reversed.

No monopole

N & S poles are always paired.
If you break a magnet in half, you will still have a N and a S
Dipole

Flux Lines

Bar magnet
Horseshoe magnet
Lines that show the direction of the field.
More lines or more densely packed lines = stronger field.

Temporary vs Permanent magnet

Passing electricity through a wire creates a magnetic field around the wire.
If you coil the wire, the field spirals around the wire.
More wires = more flux lines = stronger magnet.
Inserting an iron rod concentrates the magnetism and makes a stronger magnet.

Relationship between Moving Charges (current), Magnetism, and Force.

All three happen in three “mutually perpendicular” directions.
Thumb, pointer and middle fingers make a poorly formed gun.
Two fingers will be given as one of the three.
The third will be in the direction of the last finger.
(left hand, right hand, into or out of fingers does not matter for this course)
Example of Magnetic induction to generate a current (potential difference): a generator

A strong magnetic field between N & S poles.
A wire is pushed through the field by some force (steam, gasoline, water wheel, hand crank)
A current is produced in the wire.

Making motion: a motor

A strong magnetic field.
Current flowing through a wire which is perpendicular to the field.
A force is created in the third direction.
A coiled wire will rotate.

 


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