DelMars Electricity Unit 4 Magnetism
State three ways to demagnetize?
1. Heat 2. Strike 3. Pull away from the AC magnetic field.
What are three systems of magnetic measurement?
1. The English System 2. The CGS System 3. MKS/ SI System
Ampere - Turns
A basic unit for measurement of magnetism the product of number of turns of wire x current flow.
Electromagnets
A magnet created by electricity. It only works when surrounded by electric field
What is permeability?
A measure of a material ability to become magnetized.
Magnetic Domains
A section within a magnetic material where atoms are align to produce a north or south polarity.
What is the best permanent magnet?
Alnico5
What determines the strength of an electromagnet?
Ampere - Turns
What does current flow cause in an electromagnetic field?
An increase in the magnetic field strength.
What determines polarity of the magnetic field?
Direction of current flow through a wire.
According to the basic law of magnetism, what is required to create a magnetic field?
Energy
What are magnetic lines of force called?
Flux
Arc ferriles insulators or conductors?
Insulators
State three substance that form natural magnets?
Iron, Nickel, Cobalt
Lines of Flux
Lines of magnetic force
What are early natural magnets known as?
Loadstones
Flux
Magnetic lines of force
Where are magnetic north and south located?
Magnetic north is near the south pole. Magnetic south is near the north pole.
What are electromagnets?
Magnets that depend on current flow to produce a magnetic field.
Permanent magnets
Magnets that do not require on external force to maintain their magnetic properties.
What are permanent magnets?
Magnets that do not require power or force to maintain field.
Coercive force
Materials ability to retain magnetism.
What is reluctance?
Materials resistance to magnetism.
What are paramagnetic materials?
Materials that can be magnetized, but not as easy.
What are diamagnetic materials?
Materials that cannot be magnetized.
What are ferromagnetic materials?
Materials/metals that are easily magnetized.
Residual Magnetism
The amount of magnetism left in an object after the magnetized force has been removed.
What is the angle of declination?
The difference between true and magnetic north.
Magnetomotive Force ( MMF )
The magnetic force produced by current flowing through a conductor of coil.
Residual magnetism
The magnetism remaining in a cove material after current flow stops.
Saturation
The maximum amount of magnetic flux a material can hold.
Flux Density
The number of magnetic lines contained in a certain area. The are measurement depends on the system of measurement.
What is an ampere - turn?
The number of turns time the amount of current flow.
Electron Spin Patterns
The pattern or direction in which electrons spin as they orbit the nucleus of an atom.
What is a magnetic domain?
The section within a magnet where atoms are aligned to produce a north and south polarity.
What is significant about ferriles?
They are electrically non - conductive and ferri-magnetic meaning they can be magnetized or attracted to a magnet.
What was significant about early natural magnets?
They were self-aligning.
What is the design function of an electromagnetic?
To lose its magnetism when current flow stop.
Demagnetized
To remove magnetism from an object.
What is the resistivity of a ferrile?
10^6 ohms per centimeter.
At what temperature does iron lose its magnetism?
1420 degrees F
Permeability
A measurement of a material ability to conduct magnetic lines of flux. The standard is air, where has a permeability of one.
Left hand rule
A rule used for determining the polarity of an electromagnet when the direction of current flow is known.
What is a ferrite?
A type of ceramic compound composed of Iron, Oxide combined chemically with one or more additional metallic elements.
What is an air - core magnet?
Coil wound around a non magnetic material.
What is them most common diamagnetic material used in electrical work?
Copper
What is the left hand rule?
Determines polarity of an electromagnet when the current flow is known. The left thumb will point to magnetic north.
What is saturation?
Molecules align to a point where the material reaches magnetic capacity.
Lodestones
Natural Magnets
According to the basic law of magnetism is energy required to maintain a magnetic field?
No
Do flux lines flow?
No
What is flux density?
Number of magnetic lines contained in a certain area.
Basic Law of Magnetism
Opposite poles attract, like poles repel
Reluctance
Resistance to magnetism
