Classification of Electrical Engineering Materials

Materials used in Electrical Engineering are called Electrical Engineering materials. They are classified based on their properties and applications.

1. Conductors
2. Semiconductors
3. Insulators
4. Magnetic material

A classification chart of electrical engineering materials is shown in figure below

Conductors

Conductors are materials with very high conductivity due to the large number of free electrons at room temperature.
Examples: Silver, Copper, Gold, Aluminum etc.
Silver has a high number of free electrons, making it one of the best conductors of electricity. The nucleus has a weak binding force on these electrons, allowing them to move freely and conduct electricity.

Semiconductors

Semiconductors have conductivity between conductors and insulators. They are elements from groups III and IV with covalent bonds. At normal temperatures, their conductivity of semiconductors is low but increases rapidly with temperature.
Example: Germanium, Silicon, Gallium Arsenic etc.

Insulating Materials

Insulating materials have very low conductivity and high resistivity, making them ideal for insulating current-carrying parts from grounded metal structures. Their electrons are tightly bound to the nucleus, preventing free movement and resulting in high resistivity of insulating materials.
Example:- Plastics, Ceramics, PVC etc.

Magnetic Materials

These materials play an important role for existence of various electrical machines. The magnetic materials having high permeability are used for building the core to from the low reluctance path for magnetic flux. Magnetic materials can be further divided in following categories

• Ferromagnetic materials
• Paramagnetic material
• Diamagnetic materials
• Antiferromagnetic materials
• Ferrites

Ferromagnetic Materials

These materials are having very large and positive susceptibility to external magnetic field. They are having a strong attraction to external magnetic field and are able to retain magnetism even after removal of external magnetic field. This property of materials is called magnetic hysteresis.
Example: Iron, Cobalt, Nickel.

Paramagnetic Material

These materials are having very small and positive susceptibility to external magnetic field. In the presence of external magnetic field, these materials attain very small magnetism. Example: Aluminum, Platinum, oxygen, Air etc.

Diamagnetic materials

These materials are having very weak and negative magnetic susceptibility to external magnetic field. On application of external magnetic field these are repelled slightly by the external magnetic field. These materials do not retain the magnetism after removal of external magnetic field. Mostly all metals i.e. silver, copper, gold, hydrogen etc. are diamagnetic materials.

Antiferromagnetic materials

These materials are having a very small and positive susceptibility to external magnetic field. In the presence of external magnetic field these materials get slightly magnetized in the direction of the external magnetic field. In these materials, atoms are having mixed parallel and anti parallel aligned magnetic dipole movement.
Example: Cr, MNO, FeO, CoO, NiO, Mn etc.

Ferrites

These materials are having very large and positive magnetic susceptibility like ferromagnetic materials. These materials are generally compounds which are having more complex crystal structures than a pure material. As compared to ferromagnetic materials, ferrites are having lower magnetic saturation.
Example: Fe₃O₄, BaO.6Fe₂O₃ etc.