Magnetism Flashcards
What are lodestones?
Natural magnets
How was the first compass invented?
A piece of magnetite was placed on a piece of wood floating in the water.
Does magnetic north align with true north?
No
What is the angular difference between the true north and the magnetic north?
Angle of declination
What are permanent magnets?
Magnets that do not require any power or force to maintain their field.
What is one of the most basic laws of magnetism?
Energy is required to create a magnetic field, but no energy is required to maintain a magnetic field.
What are the three substances that form natural magnets?
Iron, nickel, and cobalt.
What is the electron theory of magnetism?
- Electrons spin on their axis which causes a small magnetic field. The electrons spin in opposite directions which causes them to cancel each other out.
- When atoms of most materials combine, they arrange in a way that cancels the magnetic field. When atoms of iron, cobalt, and nickel combine their magnetic field is added instead of cancelled.
What are the three classifications of magnetic materials?
Ferromagnetic, paramagnetic, and diamagnetic materials
What are ferromagnetic materials?
Metals that are easily magnetized. Ex. Iron, nickel, and cobalt.
What are paramagnetic materials?
Metals that can be magnetized, but not as easily as ferromagnetic materials.
What are diamagnetic materials?
Metal or nonmetal materials that cannot be magnetized. Ex. copper, brass, antimony.
What are magnetic lines of force called?
Flux
True or False. Magnetic lines of flux repel each other and sometimes cross.
False. Magnetic lines of flux repel each other and never cross.
Whenever an electrical current flows through a conductor, a __________ is formed around the conductor.
Magnetic field
What are two factors that determine the number of flux lines produced by an electromagnetic?
- The number of turns of the wire
- The amount of current flow through the wire
Strength of electromagnet is proportional to ___________
Number of ampere-turns
What is permeability?
A measurement of a material’s ability to conduct magnetic lines of flux.
What is reluctance?
A material’s resistance to magnetism
What is saturation?
The maximum amount of magnetic flux a material can hold.
What is residual magnetism?
The amount of magnetism left in a material after the magnetizing force has stopped.
If the residual magnetism of a piece of core material is hard to remove, the material has a _________
High coercive force
When is a high coercive force desirable?
When you want materials that are intended to be used as permanent magnets.
When is a low coercive force desirable?
When you want materials that are intended to be used as electromagnets.
