Chapter 4
Earth contains magnetic poles
True
A basic law of magnetism states unlike poles ____________ and like poles _____________
attract, repel
The angular difference between true north and magnetic north is known as the angle of ____________
declination
If an object is placed in the field of a strong electromagnet connected to an AC line, the object will be _____________
demagnetized
Magnetic lines of force are called _____________
flux
In the English system of measure, magnetic strength is measured in a term called _____________
flux density
The three substances that form natural magnets are ____________
iron, nickel, and cobalt
To locate to north pole of an electromagnet, use the ____________ hand rule
left
In the English system, the total force producing a magnetic field is the ______________
magnetomotive force
The north pole of a compass needle points in the direction of the south geographic pole
False
______________ do not require any power of force to maintain their field
Permanent magnets
The strength of an electromagnet is primarily proportional to its _______________
ampere-turns
Electrons can form spin patterns that __________ the magnetic field of the material
cancel
A magnet produces a magnetic field as long as current is flowing is called a(n) _____________ magnet
electromagnet
Magnetism can be explained in the term of ___________ spin patterns
electron
Man-made permanent magnets retain their magnetism _____ than natural magnets.
longer
Lodestones is the name for a naturally occurring magnetic material that is also called ______________
magnetite
The measure of a material's ability to be magnetized is called __________
permeability
The measure of a material's resistance to magnetism is _____________
reluctance
The amount of magnetism left in a material after the magnetizing force has stopped is called _____________
residual magnetism
The north magnetic pole of a compass needle is attracted to the ___________ magnetic pole of the earth
south
The regions formed in the molecular structure of magnetic metals is sometimes called magnetic ____________
domains
When a magnet's molecules are all lined up, and increases in the current flow no longer cause increases in magnetic field strength, the material has reached _________________
saturation