Magnetism And Electromagnetism Flashcards
What is a ferromagnetic material
Materials magnetized easily
(Iron,cobalt, manganese)
What is a paramagnetic material
Can be magnitized but not as easily as ferromagnetic
(Platinum,titanium,chromium)
What is a diamagnetic material?
Things that cannot be magnetized.
(Copper, brass, antimony)
What causes magnetism
An imbalance of electron spin
What is a magnetic domain
A group of atoms with all their magnetic moments in the same direction
What is magnetic moment
An electron that has a greater value than 0 of magnetism in 1 direction
What are the two types of magnets
Temporary.
Permanent
What is magnetic flux
The lines of force around a magnet
What is flux density
The concentration of lines of force around a magnet
What is permeability
Describes a material property that decides how much opposition to flux there will be
Whats the difference between high permeability and low.
High means flux easily establishes in it. Low means it does not as easily
What is reluctance
The opposition from a material to establish a magnetic path
What is retentivity
The ability for an item to retain magnetism
What is saturation
The point which all domains have been aligned and adding more current will not increase magnetism
Do electro magnets use ac or dc mainly
DC
What is the left hand rule for conductors
Curve of fingers is lines of force and thumb direction is current flow
What does a + represent in terms of current flow
Its flowing away from you
What does a dot represent i. Current flow?
Current is flowing towards you
What is the left hand rule for coils
Fingers represent current flow and thumb represents the north pole of a magnet
What direction does flux flow in a coil
From north to south pole
What affects electro magnet strength
Amount of current in the coil
Number of turns in the coil
Type of core used
If you double current in an air core coil what happens to magnetism strength
Doubles
What are the two common cores of electro magnets
Air and iron
Do we want high or low retentivity in the core of an electromagnet?
Low
What is hysteresis loss
Energy lost to friction from constantly changing poles from ac circuits in magnets
How do we reduce hysteresis loss?
Add silicone to the steel core this reduces friction
What is an eddy current
The vtage produced jn the core of an electromagnet due to the changing magnetic field
What is eddy current loss
The heat and subsequent energy lost from the currents circulating in the core of a magnet
How do we reduce eddy losses?
Making the core out of thin sheets as apposed to a solid core this reduces currents ability to flow
What do iron losses inclued
Hysterisis loss and eddy current loss measured in watts
What happens once saturation is reached?
Any extra energy is turned to heat
