Magnestism Flashcards
What is Eddy Currents
Eddy currents are a type of electrical current that is created when a conductor is placed in a changing magnetic field.
What is Theoretical saturation
Theoretical saturation in magnetism is the point at which a material can no longer be magnetized, regardless of the strength of the applied magnetic field.
What is Practical Saturation
Practical saturation in magnetism is the point at which a material can no longer be magnetized by an external magnetic field
What is Hysteresis loss
Hysteresis loss is the energy lost in a magnetic material due to the lag in magnetization when an alternating magnetic field is applied.
What is Hysteresis
The lagging of magnetic flux behind magnetic force
What is lamination used for
To prevent eddy currents
What is a form of Hysteresis loss
Heat
What material has less residual magnetism and a smaller hysteresis loop and what material is the opposite
Soft Iron and Steel
Why is soft iron better then Steel
Soft iron is better than steel for magnetism because it is more easily magnetized and demagnetized. It also has a higher permeability, which means it can hold a stronger magnetic field.
What is a ferromagnetic material
A ferromagnetic material is a material that is capable of being magnetized and can be strongly attracted to a magnetic field
What is a permanent magnet
Rare earth magnet
What material is used for electromagnets?
How did they decide which pole of a magnet is the north pole?
The end of the magnet that points North
List the six characteristics of magnetic lines of force?
- Travel North to South
- Form complete loops
- Have tension along their length
- Repel each other
- Cannot Cross
* They arrange so that
max number of line set up
What is a magnetic screen? What is it used for?
Used to deflect magnetic Flux
What’s magnetic induction?
The flux from one maget alligning domains in anther piece of ferromagnet without touching
List three methods of creating a magnet with a ferromagnetic material.
- Using Current
- Stroking Magnet
- Aligning and tapping
List three ways of removing the magnetism from a ferromagnetic material.
- Vibrations
- Heat
- Contact with an alternating current field
List four precautions to observe so you do not damage a magnet.
- Do not expose to Heat
- Do not place near AC Fields
- Do not drop or vibrate
- Do not store beside other magnets
What is the purpose of a keeper?
Used for storage, creates easier path for magnetic field while not in use
- What is the left-hand rule for conductors?
- Dot means conductor coming near you
- X means conductor going away
Draw a picture showing two conductors with current flowing through them in the same direction with their associated magnetic field? Will they attract or repel?
2 small circles in a big circle and all circles have a clockwise flow direction so they will repel by being like.
Draw a picture showing two conductors with current flowing through them in the opposite direction with their associated magnetic field? Will they attract or repel
2 circles each so 4 in total one set with both circles going clockwise other set with 2 circles going counter clockwise, they will attract as they are opposites
Why do we need to take into account the magnitude of the forces between conductors?
There are strong forces acting on conductors and busbars when a fault occurs
What is the left-hand rule for coils?
Thumb Faces Northpoles Fingers Face direction of current
List the four factors that affect the strength of an electromagnet?
- Spacing between Coil tuns
- Amount of current flowing thro coil
- Number of turns
- Type of core material
What is the most practical way of varying the strength of an electromagnet
Varying Current thro a rheostat
Define
1. Magnetic Circuit
- Path of flux lines forming their loops
Which material has more hysteresis losses? Soft Iron or Hard Steel?
Hard steel as it has a bigger hysteresis loop
How are the cores of magnetic circuits usually constructed?
From materials of high permeability and low reluctance
What type of magnetic properties do core materials usually have for AC magnetic circuits
Low retentivity to reduce reat losses and high electrical resistance to reduce eddy currents
Which type of electrical equipment uses air gaps?
Motors, Generators, and relays
Which would be preferred a large or small air gap?
Small air gap (lower reluctance)
List four applications of electromagnetic devices?
- lifting
magnets - Field Poles
- Relays
- Bells and buzzers
Lines of force start at north pole and end at south
False
The arrows on magnetic lines point north to south outside a magnet and south to north inside?
True
Which method of demagnetizing is used by watchmakers
Using electric current
Why are there no magnetic poles in a field surrounding a current carrying conductor?
There is no point of convergence or divergence of the flux lines, there is no point of flux concentration
When direction of current in conductor is reversed what happens to compasses around it?
They all reverse at the same time
As current in conductor is increases what happens to flux lines surrounding it?
Increases flux lines that then face outward
When current remains steady what happens to the field?
It becomes stationary
Do parallel conductors with currents in same direction attract or repel?
Do parallel conductors with currents in opposite direction attract or repel?
Opposite direction repels
Same direction attracts
The type of core material used for lifting magnets would have a___ retentivity
Low Retentivity
Magnetic cores are made of ?
Materials with high permeability and low reluctance
