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