Physics ~ MAGNETISM (ppt 2)

1000 BC near village of Magnesia, discovered magnetite (lodestone)

magnetism was discovered

any charged particle in motion creates a ____

magnetic field

a moving charged particle induces a magnetic field in a plane __

perpendicular to its motion

another word for elliptical is ___

circular

when a charged particle moves in a elliptical path, the perpendicular magnetic field ___

moves with the charged particle

electrons behaving as if they rotated on an axis clockwise or counterclockwise

electron spin

the electron spin creates a

magnetic field (which is neutralized in electron pairs)

atoms with have a very small magnetic field if ___

they have an odd number of electrons in any shell

a spinning charged particle will induce a magnetic field along ____

the axis of spin

the proton in a hydrogen nucleus spins on its axis and creates a ____

nuclear magnetic dipole called a magnetic moment

the lines of a magnetic field are always ____

closed loops

the small magnetic created by the electron orbit is called a ____

magnetic dipole

the lines of a magnetic field do NOT ____

start or end as the lines of an electric field do (bipolar or dipolar)

an accumulation of atomic magnets with their dipoles aligned creates a ____

magnetic domain

if magnetic domains align, ___

it acts like a magnet

external magnetic fields

the earth, naturally occurring ores, or an electromagnet

when acted on by an external magnetic field, randomly oriented dipoles ____

align with the magnetic field

if nonmagnetic material is brought near such a magnet, imaginary field lines are ___

not disturbed

if ferromagnetic material is brought near the bar magnet, the magnetic field lines ____

deviate and are concentrated into the ferromagnetic material

ability of material to attract the lines of magnetic field intensity

magnetic permeability

3 principal types of magnets

naturally occurring, electromagnets, artificially induced permanent

naturally occurring magnet example

earth (lodestone)

artificially induced permanent magnet example

usually made of iron (compass)

electromagnet example

wire wrapped around an iron core

magnets are classified according to ____

the origin of the magnetic property

artificially permanent magnets are typically produced by ___

aligning their domains in the field of an electromagnet

Permanent magnets do not stay permanent; the magnetic property can be destroyed by __

heating it or hitting it with a hammer

electromagnets are produced when ___

an electric current is conducted through the wire

an electromagnet’s magnetic field intensity is proportion to the ____

electric current

The iron core of an electromagnet greatly increases ___

the intensity of the magnetic field

all matter can be classified according to the manner in which it ____

interacts with an external magnetic field

Classification (1/4): nonmagnetic

material unaffected when brought into a magnetic field (wood, glass)

Classification (2/4): diamagnetic

materials that are weakly repelled by either magnetic pole (water, plastic)

diamagnetic materials cannot be __

artificially magnetized and are not attracted to a magnet

Classification (3/4): ferromagnetic

materials that are strongly attracted by a magnet and usually can be permanently magnetized by exposure to a magnetic field (iron, cobalt, nickel, Alnico)

classification (4/4): paramagnetic

materials that lie somewhere between ferromagnetic and nonmagnetic; slightly attracted to a magnet and are loosely influenced by an external magnetic field (contrast agents used in MRI)

degree to which a material can be magnetized

magnetic susceptibility

wood has a low magnetic susceptibility, because ___

when placed in a strong magnetic field, it does not increase the strength of the field

iron has a high magnetic susceptibility, because when placed in a magnetic field ___

it will greatly increase the strength of the field

There is no smallest unit of magnetism

true

every magnet has ___

two poles (north and south)

like magnetic poles ___, and unlike magnetic poles ____

repel, attract

the imaginary lines of the magnetic field leave the ___ pole, and return to the ___ pole

north, south

ferromagnetic objects can be made into magnets by ___

induction

if soft iron is brought into the vicinity of an intense magnetic field, the magnetic field lines of induction are ____

altered by attraction to the soft iron and the iron is made temporarily magnetic

magnetic force is proportional to the ___

product of the magnetic pole strengths divided by the square of the distance between them

SI unit of magnet field strength

tesla (T)

One tesla (T) =

10,000 gauss (G)

the earth’s magnetic field is approximately 50 µT at the ____ and 100 µT at the ____

equator, poles

if copper (diamagnetic) were to be in the vicinity of an intense magnetic field, ____

it would have no effect on the magnetic lines of induction