 Inductors are just coils of wire. Inductors are a device that temporarily stores energy in the form of a magnetic field.  It resists the sudden change in current. Current in inductor not immediately changes it lags by a certain amount of time. It is used in a circuit to block AC and allow DC current to pass. It reduces the ripple content in the current. It is also used for blocking high frequency. Strength of the magnetic field is directly proportional to number of coil inductors are similar to Capacitors as both temporarily store energy just the difference is capacitors stores electrical energy whereas Inductors store energy in the form of Magnetic energy.

There are many inductor types, here we have talked about Lead inductors, the The color codding method is only applicable in Lead inductors:

### 3 Band Inductor

It has 3  color Bands, 1st end of Band is considered as 1st significant digit, then 2nd significant digit and 3rd are Tolerance.

(1st Significant digit)  (2nd significant digit)  x   0.000001    –  Tolerence

Example:

Inductor with,

Red  =   1st Band color  =  1st significant digit

Brown = 2nd color Band  = 2nd significant digit

Black = 3rd color Band  =  Tolerance

Now we know,

If we put the value accordingly we get,

(1st Significant digit)  (2nd significant digit)  x   0.000001    –  Tolerence

2                              1                   x  0.000001    –        ± 0.20

=     21 x 0.000001     ± 20

=    21   µH   ± 0.20

### 4 Band Inductor

It has 4 color band, 1st end of band is considered as 1st significant digit, then 2nd significant digit, 3rd is multiplier and 4th color is for tolerance.

{(1st Significant digit)  (2nd significant digit)  x  multiplier}  x  (0.000001)    –  Tolerence

Example:

A Inductor with,

Red  =   1st Band color  =  1st significant digit

Brown = 2nd color Band  = 2nd significant digit

Black = 3rd color Band  =  Multiplier

Blue = 4th color band = Tolerence

Now we know,

If we put the value accordingly we get,

{  (1st Significant digit)  (2nd significant digit)  }  x Multiplier  x   (0.000001 )   –  Tolerence

2                                              1                              1           x   (0.000001)     –    ± 0.20

= 21  x 1  x (0.000001)

21 x   µH         ± 0.20

Note:   Significant digits are not to be multiplied with each other.