Magnetism Notes Flashcards
What materials do magnets attract?
Iron, nickel, cobalt and few minerals/alloys
Where is the force of a magnet strongest?
At the poles
How was the first compass made?
using magnetite on a piece of floating wood in a dish of water
What is the North pole of the compass actually referring to?
magnetic south pole of the earth
What are the three basic types of magnets?
- Natural
- Artificial
- Electromagnets
Example of Natural magnet?
Lodestone (known as magnetite)
What is Lodestone?
A natural magnet that is an oxide of iron (Fe3O4) and is still mined today
example of a permanent magnet?
Lodestone
What do artificial magnets not depend on?
an electrical current to maintain the magnetic field
difference between artificial and electromagnetic magnets?
Electromagnets magnetism depends on current flow where artificial does not
Ferromagnetic?
metals that are easily magnetized (iron, nickel, cobalt)
Paramagnetic?
metals that are not as easily magnetized (platinum, titanium, chromium)
Diamagnetic?
metals or non-metal material that can not be magnetized
One of the best alloys used for permanent magnets?
Alnico 5
What is Alnico 5 made of?
Aluminum, cobalt, nickel, copper, iron
What is magnetism caused by?
Static electrical charges (electrostatic lines of force)
What direction do flux lines flow?
They exit north and enter south
What do flux lines always do?
they always form a complete loop and never cross each other
How do flux lines pass through all materials?
Because there is no insulator
What is the property that opposes the setting up of flux lines?
reluctance
What is used to protect a delicate instrument?
a magnetic screen
What is a magnetic screen made of?
soft iron material due to low reluctance
What does a magnetic screen do to flux lines?
causes them to bend away from the instrument
What determines the amount of magnetic force?
the flux density or concentration
The greater concentration of flux lines?
the stronger the magnetic field
Flux lines facing the same direction __________ each other?
attract
Flux lines facing opposite direction ________ each-other?
repel
What happens when a magnet achieves max flux density?
It is said to be saturated
Soft iron (low carbon)?
easily magnetized but does not stay magnetized
Hard iron (high carbon)?
harder to magnetize but will remain magnetized (permanent magnet)
what are the atoms like in non magnetized metals?
disarranged
What are atoms like in magnetized metals?
arranged in an orderly fashion (called a domain)
How to produce artificial magnets?
- Using DC current
- By stroking with a magnet
- by tapping the material
What is the most effective way to produce artificial magnets?
using DC current
Common methods of demagnetizing ferromagnetic material?
- by using heat
- by vibration or tapping
- by using AC current
Most common way to demagnetize ferromagnetic material?
By using AC current to change directions from positive to negative at a rate of 60 cycles per second
Precautions to observe to avoid damaging magnets?
- don’t expose magnets to heat
- do not place magnets near fields made by AC
- do not drop or subject to vibration
- has a keeper for horseshoe magnets
- do not store magnets near other magnets
What is a keeper for?
preserves the strength of a magnet
