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Magnetism > Magnestism > Flashcards

Magnestism Flashcards

1
Q

What is Eddy Currents

A

Eddy currents are a type of electrical current that is created when a conductor is placed in a changing magnetic field.

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2
Q

What is Theoretical saturation

A

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.

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3
Q

What is Practical Saturation

A

Practical saturation in magnetism is the point at which a material can no longer be magnetized by an external magnetic field

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4
Q

What is Hysteresis loss

A

Hysteresis loss is the energy lost in a magnetic material due to the lag in magnetization when an alternating magnetic field is applied.

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5
Q

What is Hysteresis

A

The lagging of magnetic flux behind magnetic force

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6
Q

What is lamination used for

A

To prevent eddy currents

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7
Q

What is a form of Hysteresis loss

A

Heat

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8
Q

What material has less residual magnetism and a smaller hysteresis loop and what material is the opposite

A

Soft Iron and Steel

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9
Q

Why is soft iron better then Steel

A

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.

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10
Q

What is a ferromagnetic material

A

A ferromagnetic material is a material that is capable of being magnetized and can be strongly attracted to a magnetic field

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11
Q

What is a permanent magnet

A

Rare earth magnet

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12
Q

What material is used for electromagnets?

A
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13
Q

How did they decide which pole of a magnet is the north pole?

A

The end of the magnet that points North

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14
Q

List the six characteristics of magnetic lines of force?

A
  1. Travel North to South
  2. Form complete loops
  3. Have tension along their length
  4. Repel each other
  5. Cannot Cross
    * They arrange so that
    max number of line set up
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15
Q

What is a magnetic screen? What is it used for?

A

Used to deflect magnetic Flux

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16
Q

What’s magnetic induction?

A

The flux from one maget alligning domains in anther piece of ferromagnet without touching

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17
Q

List three methods of creating a magnet with a ferromagnetic material.

A
  1. Using Current
  2. Stroking Magnet
  3. Aligning and tapping
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18
Q

List three ways of removing the magnetism from a ferromagnetic material.

A
  1. Vibrations
  2. Heat
  3. Contact with an alternating current field
19
Q

List four precautions to observe so you do not damage a magnet.

A
  1. Do not expose to Heat
  2. Do not place near AC Fields
  3. Do not drop or vibrate
  4. Do not store beside other magnets
20
Q

What is the purpose of a keeper?

A

Used for storage, creates easier path for magnetic field while not in use

21
Q
  1. What is the left-hand rule for conductors?
A
  1. Dot means conductor coming near you
  2. X means conductor going away
22
Q

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?

A

2 small circles in a big circle and all circles have a clockwise flow direction so they will repel by being like.

23
Q

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

A

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

24
Q

Why do we need to take into account the magnitude of the forces between conductors?

A

There are strong forces acting on conductors and busbars when a fault occurs

25
Q

What is the left-hand rule for coils?

A

Thumb Faces Northpoles Fingers Face direction of current

26
Q

List the four factors that affect the strength of an electromagnet?

A
  1. Spacing between Coil tuns
  2. Amount of current flowing thro coil
  3. Number of turns
  4. Type of core material
27
Q

What is the most practical way of varying the strength of an electromagnet

A

Varying Current thro a rheostat

28
Q

Define
1. Magnetic Circuit

A
  1. Path of flux lines forming their loops
29
Q

Which material has more hysteresis losses? Soft Iron or Hard Steel?

A

Hard steel as it has a bigger hysteresis loop

30
Q

How are the cores of magnetic circuits usually constructed?

A

From materials of high permeability and low reluctance

31
Q

What type of magnetic properties do core materials usually have for AC magnetic circuits

A

Low retentivity to reduce reat losses and high electrical resistance to reduce eddy currents

32
Q

Which type of electrical equipment uses air gaps?

A

Motors, Generators, and relays

33
Q

Which would be preferred a large or small air gap?

A

Small air gap (lower reluctance)

34
Q

List four applications of electromagnetic devices?

A
  1. lifting
    magnets
  2. Field Poles
  3. Relays
  4. Bells and buzzers
35
Q

Lines of force start at north pole and end at south

A

False

36
Q

The arrows on magnetic lines point north to south outside a magnet and south to north inside?

A

True

37
Q

Which method of demagnetizing is used by watchmakers

A

Using electric current

38
Q

Why are there no magnetic poles in a field surrounding a current carrying conductor?

A

There is no point of convergence or divergence of the flux lines, there is no point of flux concentration

39
Q

When direction of current in conductor is reversed what happens to compasses around it?

A

They all reverse at the same time

40
Q

As current in conductor is increases what happens to flux lines surrounding it?

A

Increases flux lines that then face outward

41
Q

When current remains steady what happens to the field?

A

It becomes stationary

42
Q

Do parallel conductors with currents in same direction attract or repel?

Do parallel conductors with currents in opposite direction attract or repel?

A

Opposite direction repels
Same direction attracts

43
Q

The type of core material used for lifting magnets would have a___ retentivity

A

Low Retentivity

44
Q

Magnetic cores are made of ?

A

Materials with high permeability and low reluctance

Magnetism (1 decks)

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