Page 104 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

Valance and conduction Valance and conductor Forbidden energy gap of
bands are overlapped bands are separated by 6 to 10 ev
forbidden energy gap of
3
1.1 ev

Conductor formed using Semiconductor are Insulators are formed
metallic bonding formed due to covalent due to ionic bonding
4 bonding

Resistance is very small Resistance in high Resistance is very high

5

It has positive It has negative It has negative
temperature coefficient temperature coefficient temperature coefficient
6

Example:- Copper, Example:- Germanium, Example:- Mica, Paper
Aluminum etc. Silicon etc etc
7

Materials Used For Conductors, Semiconductors & Resistors
• Conductors are those materials that easily conduct electricity, materials with high electrical conductivity and
low electrical resistivity such as copper, iron, gold, aluminum, and silver are the best materials for conducting
electricity. Also Mercury, Steel, Iron & Seawater.
Semiconductor is that Materials with an electrical conductivity value that falls between that of a conductor and
that of an insulator such as antimony, arsenic, boron, carbon, germanium, selenium, silicon, sulfur and tellurium.
Silicon is the best known of these, forming the basis of most ICs. Common semiconductor compounds include
gallium arsenide, indium antimonide and the oxides of most metals.
• Resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or
fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the
core. Such as.
• Wire wound (WW)
• Carbon Composition (CCR)
• Carbon Film.
• Metal Film.

• Metal Oxide Film.
• Foil.
Ohm’s Law

Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage applied across
it, while inversely proportional to its resistance. In simpler terms, it relates how voltage, current, and resistance are
interconnected within an electrical circuit.

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CITS : WCS - Mechanical - Exercise 9 CITS : WCS - Mechanical - Exercise 9