CH 7

Question 1

Magnetic domain

Answer 1

A group of atoms in which the electrons have the same magnetic orientation is called a magnetic domain.

Question 2

Saturation magnetisation

Answer 2

Occurs when all the domains are aligned to the magnetic field.( Max magnetisation a material can obtain)

Question 3

Soft magnets

Answer 3

The magnetic domains become randomly oriented again once the magnetic field is removed.

Question 4

Hard magnets

Answer 4

Materials which retain the orderly domain alignment after the magnetic field has been removed.

Question 5

Coercivity

Answer 5

It is the magnetic field required to completely reverse the orientation of the magnetic domains.

Question 6

Remanence / retentivity

Answer 6

Is the amount of magnetisation a material retains when a magnetic field is removed.

Question 7

Permeability

Answer 7

This refers to the ease of magnetisation of a material when exposed to a magnetic field.

Question 8

Diamagnetic

Answer 8

Have a magnetic moment of zero.
Copper
Silver
Gold
Carbon
Alumina
Sodium chloride
Calcium chromate
All polymers

Question 9

Paramagnetic materials

Answer 9

Have a net magnet moment
Aluminium
Titanium
Lithium
Magnesium
Have un paired electrons
S P orbitals unpaired electrons = weak magnetised
D F orbitals strong magnetised.

Question 10

Ferro magnetic materials

Answer 10

Have a net magnetic moment
Iron
Nickel
Cobalt
Caused by the unfilled 3d orbital
High coercivity and magnetic permeability high remanence.

Question 11

Ferrimagnetic materials

Answer 11

Magnetic moments are due to ions
Ceramics

Question 12

Curie temperature

Answer 12

The temperature at which remanence is zero is called curie temperature.

Question 13

Inductance

Answer 13

Is the magnetic flux induced in a material in a magnetic field.