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