RESISTANCE

RESISTANCE

Conductor:

A material which gives up free electrons easily and offer little opposition resistance to flow of current is called conductor.

Example: Gold, Silver, Copper, Aluminum, Iron, Brass

Insulator:

A material which does not give up free electrons easily and offers great opposition resistance to flow of current is called insulator.

Example: Glass, Rubber, Oil, Porcelain, Ceramic

Resistance: (R)

Opposition offered to the flow of electrons in any substance is called Resistance, it is denoted by Ω and measured in ohm.

Impedance: (Z)

The impedance is the total opposition offered in the flow of current in A.C circuit. It is denoted by ‘Z’ and measured in ohm.

Resistor:

It is device, which changes electrical energy into power or heat. It is used to control the flow of current or the voltage drop across a circuit.

There are two main types

1. Fixed Resistor

2. Variable resistor

Types of Resistor:

Fixed wire wound Grid Resistor

Carbon composition Foil Resistor

Carbon film Metal Film

Printed carbon resistor Tantalum

Ceramic Phenolic

Water Resistor

Resistor Color Code: Tolerance

CODE CODE

1 Brown 8 Gray None 20%

2 Red 9 White Silver 10%

3 Orange 0 Black Gold 5%

4 Yellow

5 Green

6 Blue

7 Violet

Red 2

Green 5

Orange code is 3 means No. of zero 000

the resistance value is 25000 Ohms or 25 K Ohms

Page No. 7

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