Semiconductor Materials- Types & Properties

Semiconductors are those substances whose electrical conductivity lies in between conductors and insulators. In terms of energy band, the valence band is almost filled and conduction band is almost empty. Further, the energy gap between valence band and conduction band is very small. The¬†semiconductor has filled valence band, empty conduction band, and small energy gap … Read moreSemiconductor Materials- Types & Properties

Material Classification based on Energy Band Diagram

Band Gap Theory The Band Gap theory explains the mechanism of conductor, insulators and semiconductor regarding the movement of free electrons from valence band to the conduction band. An energy band which separates the conduction band and the valence band is called Band gap or¬†Forbidden band or Forbidden gap. Based on energy gap, the material … Read moreMaterial Classification based on Energy Band Diagram

Recombination & Trapping Processes in a Semiconductor

Recombination and trapping processes in a semiconductor Recombination is the process where an electron moves from the conduction band into the valence band so that a mobile electron-hole pair disappear. Classical mechanics requires that momentum be conserved in an encounter of two particles. Since the momentum is zero after recombination, this conservation law requires that … Read moreRecombination & Trapping Processes in a Semiconductor

Soft and Hard Magnetic Materials

Soft Magnetic Materials These materials are easy to magnetise and demagnetise. These materials favour rapid switching (it means high frequency) of magnetism to applied ac field. These materials have low retentivity. Low coercivity. High permeability High magnetic saturation Low hysteresis losses because of the lesser area of the hysteresis loop. These materials are used for … Read moreSoft and Hard Magnetic Materials

Magnetic Properties of Materials | Types of Magnetism

Magnetic field The Magnetic field is a force which is generated due to energy change in a volume of space. A magnetic field is produced by an electrical charge in motion e.g. current flowing in a conductor, orbital movement and spin of electrons. The magnetic field can be described by imaginary lines as shown in … Read moreMagnetic Properties of Materials | Types of Magnetism

Electrical Engineering Materials: Assertion/Reason Questions

Each of the following questions consists of two statements, one labelled ‘Assertion (A)’ and the other labelled the ‘Reason (R)’. Examine the two statements carefully and decide if the Assertion (A) and Reason (R) are individually true and if so whether the Reason (R) is the correct explanation of the Assertion (A). Select your answers … Read moreElectrical Engineering Materials: Assertion/Reason Questions

Insulating Materials for Cables & Electronic Equipments

Insulating Materials for Cables The insulating materials (dielectrics) used for cables must have low discharge current, low dissipation factor (low loss tangent), and should be chemically stable. The materials generally used are impregnated paper, bituminous compounds, rubber, compressed air, mineral oil etc. In the present days, cross-linked polyethylene cables (XLPE) are manufactured for 11 kV, … Read moreInsulating Materials for Cables & Electronic Equipments

Electrical Machine Insulation

In electrical machines, the insulation system must withstand the high electrical stresses and severe mechanical stresses induced by the magnetic field of the moving rotor. In machines, multi-turn windings are put in narrow armature slots, which are usually grounded. Rotating machine stator insulation construction is divided into principal types: Random wound conductor machines with small … Read moreElectrical Machine Insulation

Insulating Materials for Power & Distribution Transformers

The insulating materials used in power and distribution transformers must possess the following properties: Good electrical properties to withstand the power frequency (50 Hz) voltages and impulse overvoltages. Good mechanical properties to withstand fabrication and handling during manufacture and electromagnetic forces during overload, short circuit, and normal operating conditions. Good thermal stability and low ageing … Read moreInsulating Materials for Power & Distribution Transformers

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