4 Fundamentals of Electricity: Unit 4 - Magnetism
Magnetic _____ _____ _____ repel each other and never cross.
lines of flux
A piece of _____ placed on a piece of wood floating in water, always aligns itself north and south.
lodestone (or magnatight)
In theory, each molecule of a _____ _____ is itself a small magnet.
magnetic material
The two factors that determine number of flux lines produced by an electromagnet are _____ and _____.
number of turns; amount of current
Like magnetic poles _____.
repel (Law of Magnetism or Law of Charges)
If the conductor is wound into a coil the magnetic lines of flux add to produce a _____ magnetic field.
stronger
The ____ electrons in a piece of iron account for its magnetic properties.
4
One of the best permanent magnet materials is _____.
Alnico 5
_____ _____ is a measure of a material's ability to retain magnetism.
Corrosive force of retentively or residual magnetism
_____ _____ are either metal or nonmetal materials that cannot be magnetized.
Diamagnetic materials
_____depend on electrical current flow to produce a magnetic field.
Electromagnets
Electricity was first discovered by the _____.
Greeks
In the CGS system of measurement, one magnetic line of force is known as a _____.
Maxwell
_____ _____ are magnets that do not require any power or force to maintain their field.
Permanent magnets
_____ is a measure of a material's ability to become magnetized.
Permeability
_____ is resistance to magnetism.
Reluctance
One Weber = _____ lines of flux.
a hundred million (10 to 8th power)
When a coil is wound around wood or plastic, it is known as an _____ _____.
air core
Opposite magnetic poles _____.
attract
In the _____ _____, the strange powers of the magnet were believed to be caused by evil spirits or the devil.
dark ages
The electron spin theory of magnetism is based on the theory of _____ _____ _____.
electron spin pattern
Magnetic lines of force are called _____.
flux
The reason that the _____ poles are called north and south is because the north pole of a compass needle points in the direction of the north _____ pole.
geographic; geographic
A magnet can be demagnetized with _____, _____, or _____.
heat, A/C magnetic field or striking it.
When a coil is wound around a magnetic material, it is called an _____ _____.
iron core