chapter 4 basic electrical
A basic law of magnetism states that unlike poles _____ and like poles _____.
attract; repel
The angular difference between true north and magnetic north is known as the angle of _____.
declination
Of the three basic classifications of magnetic materials, _______________ materials are either metal or nonmetal materials that cannot be magnetized.
diamagnetic
Magnetic lines of force are referred to as _____.
flux
In the English system of measure, magnetic strength is measured in terms of _____.
flux density
If a permanent magnet is cut into pieces, each piece _____ a separate magnet.
is
To locate the north pole of an electromagnet, use the _____-hand rule.
left
What type of magnets do not require any power or force to maintain their field?
permanent magnets
Of the three basic classifications of magnetic materials, _______________ materials are metals that are most easily magnetized.
Ferromagnetic
The three substances that form natural magnets are _____.
diron,nickel, and cobalt
The regions formed in the molecular structure of magnetic metals are sometimes called magnetic _____.
domains
Earth contains magnetic poles.
true
The north pole of a compass needle points in the direction of the south geographic pole.
true
Man-made permanent magnets retain their magnetism _____ than natural magnets.
longer
In the English system, the total force producing a magnetic field is the _____.
maganetomotive force
The strength of an electromagnet is primarily proportional to its _____.
ampere-turns
If an object is placed in the field of an strong electromagnet connected to an AC line, the object will be _____.
demagnetized
Magnetism can be explained in terms of _____ spin patterns.
electron
Lodestone is a name for a naturally occurring magnetic material that is also called _____.
magnetite
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
What type of magnet depends on flowing current to produce a magnetic field?
electromagnet
The measure of a material's ability to be magnetized is called _____.
permeability
The measure of a material's resistance to magnetism is known as _____.
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