to find the resistance of a resistor using colour coding

1. decimal multiples and submultiples
Factor Prefix Symbol
1024 yotta Y
1021 zetta Z
1018 exa E
1015 peta P
1012 tera T
109 giga G
106 mega M
103 kilo k
102 hecto h
101 deka da

2. decimal multiples and submultiples
Factor Prefix Symbol
10-1 deci d
10-2 centi c
10-3 milli m
10-6 micro µ
10-9 nano n
10-12 pico p
10-15 femto f
10-18 atto a
10-21 zepto z
10-24 yocto y

3. RESISTOR
colour CODING

4.  Any material that offers resistance to the
flow of electric current is called resistor. A
resistor is an electronic component which
has been manufactured with a specific
value of resistance. It is used in the circuit
mainly to limit the current, to produce a
desired voltage drop and to divide the
voltage to different values from a single
source.
 The unit of resistance is ohm was named
after George Simon Ohm. He then created

6. 1.FIXED RESISTOR – Is a
device in which the value
cannot be changed readily
while in use or a resistor with
fixed value.
2.VARIABLE RESISTOR – Is a
device in which value can be
changed while in use.

7. TYPES OF RESISTORS
FIXED RESISTOR VARIABLE RESISTOR

8. Resistor colour Code
 Manufacturers typically use a colour
band system known as the resistor
colour code
 Within this power point, you will learn
how to identify the nominal resistance
and the tolerance of a resistor

9. Resistor colour Code
 The power rating is not indicated in the
resistor colour code and must be determined
by experience using the physical size of the
resistor as a guide.
 For resistors with 5% or 10% tolerance, the
colour code consists of 4 colour bands.
 For resistors with 1% or 2% tolerance, the
colour code consists of 5 bands.

10. FOUR colour BAND
RESISTOR
Resistors with four
colours on its body.
The first three colour
bands give the value of the
resistor and the last colour
represents the tolerance
value.

11. 4-Band Resistors
The resistor nominal value is encoded in the colour code in
Powers of Ten Notation. The template for determining the
nominal value and tolerance of a resistor with 4 colour bands is
given below:
1st Band =
1st Significant Digit
2nd Band =
2nd Significant Digit
3rd Band =
Multiplier
4th Band =
Tolerance
___ ___  10    ____ %

12. How do we know which colour
corresponds to which number?
Answer: Using the Resistor colour Code Table

13. Resistor colour Code Table

14. Colour code memory aid:
B B ROY Got Beautiful
Very Good Wife wearing
Gold Silver Necklace

15. Example 1. Determine the nominal resistance value and the
tolerance for the resistor shown below.
Solution:
Nominal value = 10102
= 1,000
Tolerance = 5%.
___ ___  10    ____ %
1
Brown =1
0
Black =0
2
Red =2
5
Gold = 5%

16.  It is typical to express the resistance value in:
k if the resistance  1,000
M if the resistance  1,000,000.
 To convert from  to k,  to M, or vice-versa, use the table
below:
 In the previous example we would say the resistor has a
nominal value of:



k
1
000
,
1
000
,
1

17. Example 2. a) Determine the nominal value and tolerance for the
resistor below.
b) What is the minimum resistance value this resistor
can actually have?
c) What is the maximum resistance value this resistor
can actually have?
Solution:
___ ___  10    ____ %
Resistor nominal value = 47103
= 47,000
= 47k.
Yellow =4
4
Violet =7
7
Orange =3
3
Gold = 5%
5
Tolerance = 5%

18. Solution: continued
 Minimum resistance value:
Multiply the nominal value by the tolerance and then subtract
this from the nominal value:










k
k
k
k
k
65
.
44
35
.
2
47
05
.
0
*
47
47
 Maximum resistance value:
Multiply the nominal value by the tolerance and then add this to
the nominal value:










k
k
k
k
k
35
.
49
35
.
2
47
05
.
0
*
47
47

19. Example 3. a) Determine the nominal value and tolerance for the
resistor below.
b) What is the minimum resistance value this resistor
can actually have?
c) What is the maximum resistance value this resistor
can actually have?
Solution:
___ ___  10    ____ %
Resistor nominal value = 39105
= 3,900,000
= 3.9M.
Orange =3
3
White =9
9
Green =5
5
Silver = 10%
10
Tolerance = 10%

20. Solution: continued
 Minimum resistance value:
nominal value – nominal value * tolerance:










M
M
M
M
M
51
.
3
39
.
0
9
.
3
1
.
0
*
9
.
3
9
.
3
 Maximum resistance value:
nominal value + nominal value * tolerance:










M
M
M
M
M
29
.
4
39
.
0
9
.
3
1
.
0
*
9
.
3
9
.
3

21. 5-Band Resistors
 For resistors with 1% or 2% tolerance, the colour code
consists of 5 bands.
1st Band =
1st Significant
Digit
2nd Band =
2nd Significant
Digit
3rd Band =
3rd Significant
Digit
4th Band =
Multiplier
5th Band =
Tolerance
___ ___ ___  10    ____ %
 The template for 5-band resistors is:

22. Example 4. Determine the nominal resistance and tolerance for
the resistor shown below.
Resistor nominal value = 100101
= 1,000
= 1k.
___ ___ ___  10    ____ %
Brown = 1
1
Black =0
0
Black = 0
0
Brown = 1
1
Red =  2%
2
Tolerance = 2%
Solution:

23. Example 5. Determine the nominal resistance and tolerance for
the resistor shown below.
Resistor nominal value = 680103
= 680,000
= 680k.
___ ___ ___  10    ____ %
Blue = 6
6
Gray = 8
8
Black = 0
0
Orange = 3
3
Brown =  1%
1
Tolerance = 1%
Solution:

24. Which side of a resistor do I
read from?
 A question that often arises when reading the colour
code of real resistors is: how do I determine which
side of a resistor do I read from?
Answer:
 For 4-band resistors a gold or silver band is always
the last band.
 If the resistor has 5 bands or if there is no tolerance
band (20%), then the first band is the one located
closest to a lead.

25. Converting the Nominal Resistance and
Tolerance into the colour Code
We are given the nominal value and the tolerance and we
have to come up with the colour code.
1. Resistors with 5% and 10% Tolerance will have 4-bands
4-Band Resistors
2. Convert nominal value to ohms ()
3. 1st digit (from left to right) of nominal value = 1st colour band
4. 2nd digit of nominal value = 2nd band
5. Number of zeros remaining = 3rd (multiplier) band
6. Tolerance = 4th band

26. Example 6. Specify the colour code of a resistor with nominal value
of 27k and a tolerance of 10%.
Solution:
2 7 , 0 0 0 
2) Convert the nominal resistance value to  from k.
1) Since resistor Tolerance = 10% it will have 4-bands.
Violet = 7
Red = 2 Orange = 3 10%

27. Example 7. Specify the colour code of a resistor with nominal value
of 1.5k and a tolerance of 5%.
Solution:
1 , 5 0 0 
2) Convert the nominal resistance value to  from k.
1) Since resistor Tolerance = 5% it will have 4-bands.
Green = 5
Brown = 1 Red = 2 5%

28. Converting the Nominal Resistance and
Tolerance into the colour Code
1. Resistors with 1% and 2% Tolerance will have 5-bands
5-Band Resistors
2. Convert nominal value to ohms ()
3. 1st digit (from left to right) of nominal value = 1st colour band
4. 2nd digit of nominal value = 2nd band
5. 3rd digit of nominal value = 3rd band
6. Number of zeros remaining = 4th (multiplier) band
7. Tolerance = 5th band

29. Example 8. Specify the colour code of a resistor with nominal value
of 2.5M and a tolerance of 1%.
Solution:
2 , 5 0 0 , 0 0 0 
2) Convert the nominal resistance value to  from M.
1) Since resistor Tolerance = 1% it will have 5-bands.
Green = 5
Red = 2
Yellow = 4 1%
Black = 0

30. Congratulations!
You now know how to work
with the resistor colour code
It’s that simple!