RESISTORS

A Resistor is an Electrical component which limits or regulates the flow of current.The Resistor's ability to reduce the current is known as 'Resistance'. Resistance is measures in ohms(Ω).

Resistance value is stable over a wide range of environmental conditions.

 We can also say that The resistance 'R' of a resistor is equal to the resistivity 'ρ'  times the resistor's length 'l' divided by the resistor's cross sectional area 'A'.
 

The term Resistor is derived from ohm’s law .Ohm's Law: 

According to ohm’s law Current is directly proportional to voltage.
V∝ I
V=IR , and R=V/I
Here 'R' is the resistance which opposes the flow of current.
Carbon or metal film resistors are the most commonly used resistors.

How to find resistance of a Resistor?

Each Resistor has different type of colors on it .By make use of these colors we can calculate the resistance value of a Resistor.There are 3 types of color codes for a resistor:
1)4 band Resistor
2)5 band Resistor
3)6 band Resistor

Color code for  4 Band Resistor:

In a Four band Resistor 4 Bands make the resistance value.
 Band 1-digit
Band 2-digit
Band 3-multiplier
Band 4- tolerance

The first two bands will take the digit values according to

Black

0

Brown

1

Red

2

Orange

3

Yellow

4

Green

5

Blue

6

Violet

7

Gray

8

White

9

You can also remember them as"BB ROY of Great Briton has Very Good Wife".

The 3rd band(multiplier) is color coded as follows:
black – x1        brown – x10       red – x100
orange – x1K   yellow – x10K   green – x100K
blue – x1M      violet – x10M    grey – x100M
white – x1G      gold – .1           silver – .01

The color code for tolerance is as follows:
brown – 1% red – 2% orange – 3%
yellow – 4% green – .5% blue – .25%
violet – .1% gray – .05% gold – 5%
silver – 10%If the value of resistance is 470 ohm and the 4th band of the resistor was silver(10%) ,then the value range would be resistance value+/- 10% = 460 to 480.

Here in the above example The 4 bands of the resistor are
Brown, Black, Red, Green
(Brown=1),(Black=0),(Red=2)
Tolerance(Green) = ±0.5%
Resistance value=10 x 100 = 1k ohm

Color code for  5 Band Resistor:

In a Five band Resistor 5 Bands make the resistance value.
Band 1-digit
Band 2-digit
Band 3-digit
Band 4-multiplier
Band 5- tolerance

                                               
Here the 5 bands of the resistor are
Red,Red,Black,Red,Gold
red=2,Red=2,Black=0,red=100
Tolerance(gold)=5%                                         Resistance value=220X100=22K ohm

Color code for  6 Band Resistor:

In a Six band Resistor 6 Bands make the resistance value.
Band 1-digit
Band 2-digit
Band 3-digit
Band 4-multiplier
Band 5-tolerance
Band 6-temperature coefficient

Here we have 6 bands of resistor are  Yellow,Brown,Red,Orange,Brown,Violet Resistance=412X1000=412k Ohm

Also Know about: Capacitors