Magnestism

Question 1

What is Eddy Currents

Answer 1

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

Question 2

What is Theoretical saturation

Answer 2

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.

Question 3

What is Practical Saturation

Answer 3

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

Question 4

What is Hysteresis loss

Answer 4

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

Question 5

What is Hysteresis

Answer 5

The lagging of magnetic flux behind magnetic force

Question 6

What is lamination used for

Answer 6

To prevent eddy currents

Question 7

What is a form of Hysteresis loss

Answer 7

Heat

Question 8

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

Answer 8

Soft Iron and Steel

Question 9

Why is soft iron better then Steel

Answer 9

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.

Question 10

What is a ferromagnetic material

Answer 10

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

Question 11

What is a permanent magnet

Answer 11

Rare earth magnet

Question 12

What material is used for electromagnets?

Question 13

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

Answer 13

The end of the magnet that points North

Question 14

List the six characteristics of magnetic lines of force?

Answer 14

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

Question 15

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

Answer 15

Used to deflect magnetic Flux

Question 16

What’s magnetic induction?

Answer 16

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

Question 17

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

Answer 17

1. Using Current
2. Stroking Magnet
3. Aligning and tapping

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the purpose of a keeper?

Answer 20

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

Question 21

13. What is the left-hand rule for conductors?

Answer 21

1. Dot means conductor coming near you
2. X means conductor going away

Question 22

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?

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What is the left-hand rule for coils?

Answer 25

Thumb Faces Northpoles Fingers Face direction of current

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Varying Current thro a rheostat

Question 28

Define 1. Magnetic Circuit

Answer 28

1. Path of flux lines forming their loops

Question 29

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

Answer 29

Hard steel as it has a bigger hysteresis loop

Question 30

How are the cores of magnetic circuits usually constructed?

Answer 30

From materials of high permeability and low reluctance

Question 31

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

Answer 31

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

Question 32

Which type of electrical equipment uses air gaps?

Answer 32

Motors, Generators, and relays

Question 33

Which would be preferred a large or small air gap?

Answer 33

Small air gap (lower reluctance)

Question 34

List four applications of electromagnetic devices?

Answer 34

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

Question 35

Lines of force start at north pole and end at south

Answer 35

False

Question 36

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

Answer 36

True

Question 37

Which method of demagnetizing is used by watchmakers

Answer 37

Using electric current

Question 38

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

Answer 38

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

Question 39

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

Answer 39

They all reverse at the same time

Question 40

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

Answer 40

Increases flux lines that then face outward

Question 41

When current remains steady what happens to the field?

Answer 41

It becomes stationary

Question 42

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

Answer 42

Opposite direction repels Same direction attracts

Question 43

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

Answer 43

Low Retentivity

Question 44

Magnetic cores are made of ?

Answer 44

Materials with high permeability and low reluctance