Resistor Color Codes : How to calculate resistance of resistors using color codes?

What is a resistor?

The resistor is a passive two terminal electronic component that provides electrical resistance and used to limit or regulate the flow of electrical current in the electronic circuit. It also acts as a protection device in a circuit. The role of resistor is to reduce current flow, operation, adjusting signal levels, and dividing the voltage.

The SI unit of resistance is Ohm and the resistance given by the resistor is measured in Ohms. 

Resistance

Resistance is a measure of opposition to the electrical current flow in the circuit. The value of resistance vary from few ohms to large .

The resistors are used in various applications ranging from small circuit boards to large circuits. It includes amplifiers, oscillators, transmitters, generators, modulators, etc.

Why we require resistor color coding?

The value of the resistance is not printed on any resistor. Hence, the knowledge of resistor color code is essential to determine the value of the resistance. It is also used to predict the tolerance of a resistor. Every resistor has unique combinations of the color bands. The resistor color coding is an easy method to find the resistance value quickly.

Every circuit has its limitations of resistance. It is essential to use a resistor according to the high or low required resistance value.

How to Read Resistor color code?

The values of resistors are determined by color band marked on the resistor body. The color code marking system has been adopted by the Electronics Industries Association (EIA) and the United States Armed Forces and recognized throughout the world.

The general purpose carbon film resistors which are used in electrical and electronic circuits are marked using a four colored bands system. The first three bands determine the value of the resistor. The first two bands determine the value of the resistor and the third band determines the multiplier for the first two digits. The 4th color band indicates the resistor’s tolerance. If 4th color band is Gold that means the resistor is within 5% plus or minus of the marked value. A silver 4th color band indicates a 10% tolerance. 

4 Band Resistor Color Code :


Example 1:
Convert resistor color bands into a numerical resistor value :

Resistor color bands : Green, Blue, Orange, Gold

The first two color bands represents the number digit.
The first two color bands signify the digit at tens and one place.
Green = 5
Blue = 6

The third digit represents the multiplier for the first two digits.
Orange = 10^3 i.e; 1000

The 4th color band indicates the resistor’s tolerance.
Gold = 5% 

Therefore the value of this resistor is 56 kilo Ohms.
 
Example 2: 
Convert a numerical resistor value into the correct color bands:

What are the color bands on a 20 kΩ resistor with a 5% tolerance?

 First convert from kilo-Ohms to Ohms 20 kΩ = 20 000 Ohms.
Look at the first digit is 2. From color code chart  Red = 2, this will be first color band on the left.

The next digit after number 2 is 0 and Black = 0 , this will be the second color band 

What remains is 000, the third digit is multiplier. The Orange color represents third color band.

The fourth band is the tolerance, which is 5%. This is represented by the color Gold.  



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