Delmar Unit 4
The three substances that form natural magnets are _____.
iron, nickel, cobalt
When a coil is wound around a magnetic material such as iron or soft steel it is called an _____ _____.
iron-core magnet
Saturation occurs when all the molecules of the magnetic material are
lined up
Ampere-turns are determined by
multiplying the number of turns of wire by the current flow
What type of magnets do not require any power or force to maintain their field?
permanent magnets
____ is the measure of a materials ability to become magnetized
permeability
The three factors that determine the strength of a magnetic
Turns, current flow, and adding a magnetic material to the center of the coil
how can the polarity of an electromagnet be determined if the direction of current flow is known
Using the left-hand rule
When a magnetic material's molecules are all lined up, and increases in current flow no longer cause increases in magnetic field strength, the material has reached _____.
saturation
Lodestone is a name for a naturally occurring magnetic material that is also called _____.
Magnetite
A basic law of physics states that whenever ____ current flows through a conductor, a magnetic field is formed around the conductor
electric
____ materials are metals that are easily magnetized
ferromagnetic
The north magnetic pole if the earth is ____ polarity
south
____ materials are metals that can be magnetized but not as easy as ferromagnetic materials
Paramagnetic
unlike poles ____________ and like poles ____________.
attract, repel
____ is the measure of materials ability to retain magnetism
coercive force
the base material is called the ____
core material
The angular difference between true north and magnetic north is known as the angle of _____.
declination
____ materials are either metal or nonmetal materials that cannot be magnetized
diamagnetic
The regions formed in the molecular structure of magnetic metals are sometimes called magnetic _____.
domains
____ is the measure of the density of the field lines around a magnet
flux density
The type of core material used in an electromagnet can ____ its strength
increase
Early natural magnets were known as
lodestone
Electromagnets depend on electric current flow to produce a
magnetic field
____ can be explained in terms of electron spin patterns
magnetism
The ____ magnetic pol of a compass needle is attracted to the south magnetic pole of earth
north
The direction of current flow through the wire determines the ____ of the magnetic field
polarity
An object can be demagnetized by placing it in an AC magnetic field and _____
pulling it away, by striking and by heating
____ is the resistance to magnetism
reluctance
_____ is the magnetic flux remaining in the magnetized element
residual magnetism
Another term that is used to describe a materials ability to retain magnetism is
retentivity
When a coil is wound around a non magnetic material such as wood or plastic it is known as an
air-core magnet
Three different systems are used to measure magnetic values
The english system The CGS system The SI system
The strength of an electromagnet is proportional to its ____
ampere-turns
An increase in current flow causes
an increase in magnetic field strength
What type of magnet depends on flowing current to produce a magnetic field?
electromagnet
Magnetism can be explained in terms of _____ spin patterns.
electron
____ can form spin patterns that cancel the magnetic field if the material
electrons
Magnetic lines of force are called
flux
magnetic strength is measured in terms of _____.
flux density
Magnetic lines of flux ____ and never cross
repel
