148 Engineering Fundamentals
Goodheart-Willcox PublisherhlibP G dh t Will
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 8-15.
This resistor color
code chart shows the
numerical values and
tolerances for resistor
color stripes.
Control Components
Control devices direct and/or limit current
fl ow so a circuit meets its desired function. For
example, insulators keep current in the conduc-
tor and protect against shorts, and resistors limit
current fl ow to protect sensitive components.
Insulators
Materials with extremely high resistance that do
not conduct electricity under normal circumstances
are insulators. The most commonly used insulators
are plastic, glass, paper, rubber, and mica. Insulators
are used to keep electricity confi ned to the desired
circuit path and away from people and other parts
of the circuit. A short circuit can be defi ned as an
undesired path to ground. In a short circuit, electric-
ity is able to neutralize its charge without having
to fl ow through the load. Without the resistance
provided by the load, current increases dramati-
cally, which can cause a fi re or other damage.
Resistors
The resistor is one of the most common
and reliable electrical components. Resistors are
used to limit current fl ow and divide voltage
in a circuit. Resistors come in a variety of sizes,
shapes, and confi gurations. Most are made from
carbon. Resistors are available in values ranging
from less than one ohm to many millions of ohms.
A system of color-coding resistors with their
values was developed because it is not always
possible to print values on very small resistors.
Resistors typically have three or four (sometimes
fi ve) color bands. The fi rst two colors represent
digits. The third band is the multiplier and tells
what power of ten the digits should be multiplied
by. The fourth band is the tolerance, which indi-
cates the accuracy of the resistor value. If there is no
fourth band, a twenty percent tolerance is assumed.
On a fi ve-band resistor, the fi rst three are digits, the
fourth is the multiplier, and the fi fth is the tolerance.
Look at the resistor color code chart in
Figure 8-15. Think of a resistor whose color bands
from left to right are green, blue, brown, 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.