Copyright Goodheart-Willcox Co., Inc.
234 Engineering Fundamentals
Look at the resistor color code chart in
Figure  11-15. Think of a resistor whose color
bands from left to right are green, blue, brown,
and silver.
The fi rst two colors represent digits. The digit
for green is 5 and the digit for blue is 6. Place these
two numbers next to each other and you have 56.
The third band is the multiplier and in this case it
is brown, which has a value of 10.
So now we have 56 × 10 = 560. This is referred
to as a 560 Ω resistor.
The fourth band is the tolerance and in this
case it is silver, which has a value of 10%. This
means that the measured value of this resistor
could be 10% above or below 560 Ω.
In order to fi nd 10% of 560, do the following:
560 × 0.1 = 56
560 – 56 = 504
560 + 56 = 616
The measured value of this 560 Ω resistor
with a 10% tolerance could be anywhere between
504 Ω and 616 Ω.
See Workbook Activity 11-10 for practice
working with the resistor color code.
Variable Resistors
At times, such as in dimmer switches and fan
speed switches, it is important to vary the amount
of resistance. In these situations, resistors whose
resistance can be changed, known as variable
resistors, are used. Variable resistors have two
terminals and a wiper, which is a knob or a slid-
ing switch. As the wiper moves along a piece of
resistive material, usually carbon, the amount of
resistive material between the terminals changes,
and so does the resistance. Note the arrow on
the schematic for variable resistors. An arrow on
a schematic indicates that its value is variable.
Figure 11-16 shows common variable resistors.
First Band
1st Digit
Color Digit
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9
Second Band
2nd Digit
Color Digit
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9
Third Band
Multiplier
Color Multiplier
Black 1
Brown 10
Red 100
Orange 1,000
Yellow 10,000
Green 100,000
Blue 1,000,000
Silver 0.01
Gold 0.1
Fourth Band*
Resistance Tolerance
Color Tolerance
Silver ± 10%
Gold ± 5%
*No Band ± 20%
green blue brown silver
5 6 10 ± 10%
560 Ω ± 560 Ω
504 Ω–616 Ω
Figure 11-15. 
This resistor color code
chart shows the numerical
values and tolerances for
resistor color stripes.
Goodheart-Willcox Publisher