Conductor, Insulator and Semiconductor

Conductor, Insulator and Semiconductor

Conductor: Conductor is material which allows the flow of electric current. Conductors have free electron and provides low resistance in the flow of electric current. Conductors have valence shells containing one, two or three electrons. Example: Silver, copper, aluminum, brass, zinc, iron, steel, lead, tin, eureka, nichrome, tungsten, nickel, platinum, carbon and mercury.

Properties of a good conductor:

(1) It should have high conductivity.
(2) It should have a low specific resistance.
(3) It should have a sufficient tensile strength.
(4) It should be available at a reasonably low cost.
(5) It should have a high temperature coefficient.
(6) It should be easily joined and soldered.
(7) It should be available in large quantity.
(8) It should not be much affected by the changing atmospheric and chemical effect.

Solid conductors: A single wire is known as single conductor. It is available in different diameter. It is used in cable and overhead lines. It is usually made of copper, aluminum and steel.
Stranded conductors: The group of conductors of small diameter with respect to solid conductor is called stranded conductor. In stranded conductor 1,17,19,37 strands having 1.13 to 3.37 mm diameter are used. It has flexible and consequent properties so generally used.
Multistranded conductors: These have smaller diameter with respect to stranded conductors. These are mostly used in multistranded wires and cables. These have 14, 22, 42 and 84 strands of each having 0.2 or 0.3 mm diameter.
Flexible conductors: These have smallest diameter. The numbers of conductors in flexible conductors are 14, 23, 40 and having diameter of less than 0.2mm.

Materials which have low resistance, they have high conductance and vice versa.

Materials which have high dielectric strength they have high insulation resistance and vice versa.

Insulator: insulator is a material which does not allow the flow of electric current. Insulators does not have free electron and provides high resistance (measured in mega ohms) in the flow of electric current. Insulators have valence shells containing five, six or seven electrons. Example: Dry air, Bakelite, porcelain, mica, vulcanized rubber, polyvinyl chloride (PVC), glass, dry wood, plastic, asbestos, mica, insulating oil, paper, and varnish.

Properties of good Insulator:

(1) It should have a high resistance.
(2) It should have a high dielectric strength.
(3) It should be moisture and water proof
(4) It should be easily molded in any shape and size.
(5) It should have a large mechanical strength
(6) It should have a low cost and easily available.

Insulation resistance: It is the electrical resistance of the insulation against the flow of current. Megohmmeter (Megger) is the instrument used to measure insulation resistance. It measures high resistance values in megohms without causing damage to the insulation. The measurement serves as a guide to evaluate the condition of the insulation.

Dielectric strength: It is the measure of how much potential difference the insulation layer can withstand without breaking down. The potential difference that causes a breakdown is called the breakdown voltage of the insulation. It is measured in KV (kilo volt).

Semiconductor: Semiconductor is a material which is neither a conductor nor an insulator. Semiconductors have valence shells containing four electrons. Example: Germanium and Silicon. Semiconductors are used to produce modern electronic components such as diodes, transistors and integrated circuit chips.