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Resistors are identified by a color code used in several bands around the resistors. There are two
general types of resistors. One, the uninsulated type, has the connecting wires bound around the ends.
The other, the insulated type, has the wire connected internally and coming out the ends. The resist-
ance code uses three bands or colors, while a fourth, usually silver or gold, indicates the tolerance. The
colors are arranged so that the first two indicate the first two figures of the resistance, while
the third indicates the number of digits (zeros or multiplier) which follow the first two figures
On w1insulated resistors, the body is the first figure, the end color the second figure, and the
dot the number of digits. On insulated resistors, the band nearest the end is the first figure
the next band is the second figure and the third band the number of digits.
WATTAGE. Resistors are rated as to wattage (power dissipation) according to size.
The chart shows approximate sizes which vary with manufacturers. To determine wat-
tage size necessary multiply current through resistor in, amperes by voltage drop across
resistors in volts. Example - A plate loading resistor for a tube drawing 10 milli-
amperes (.01 Amperes) has a voltage on one side of 300 volts and on the other side
200 volts, giving a drop of 100 volts. Therefore 100 volts X .01A. = 1 Watt.
A higher wattage resistor can always be substituted for smaller size.
-fDI
=1m
~.~,
V2.W
1 W.
2W.
WATTAG E SIZES
Un insulated Body Color End Color Dot Color UNINSUL-RTED Examples INSULATED TYPE
Insulated First Ring Second Ring Third Ring TYPE; Forth. Band
-Fo,.. To/etance
Color lrKt Figure "eeond Figure Number of Digits
Black None
Brown
Red
Orange 000
Yellow 000
Green 00.000
Blue 000.000
Violet 000.000 BROWN RED ORANGE BROWN RED ORANCJE
Grey 00.000.000 000 000
White 000.000,000
Some Popular Si zes Resistors
RESISTANCE IN
250
1500
30,000
220 000
1 Megohm
OHMS BODY OR FIRST
Green
Red
Brown
Orange
Red
Brown
BANI) DOT OR THIRD
Black
Brown
Hed
Orange
Yellow
Green
BilND
BAND F)ND OR ';COND
Black
Gre.'n
Grf'en
Black
Hed
Black
The fourth ring or other end may be silver (10% tolerance) or gold (5%
tolerance) or it may be omitted entirely which indicates 20% toho rance.
Condenser Code
Condensers use the same code as resistors and are read in micromicrofarads.
If there is one row of dots, they are read in direction of arrow or if manufacturer s name appears in the same direction as
name. If two rows of dots appear, it can either be of two different codes: The RMA or the A WS (American War Standard).
In the RMA, the top row of dots are the first three figures (carried to three figures), the bottom row are left to right the voltage
rating, tolerance, and decimal multiplier.
In the A WS code, the top row of dots are the first three figures while the bottom row are, left to right, characteristic
tolerance, and decimal multiplier. Examples
RMA
=;IJft=
'BROWN RED GREEN BROWN
12~O MMF = OOI25MF
AVVS
RED GREEN BROWN
"2.
ZSO MMF
=' .
0002.5 MF
1t.:.& DOT
A LWAVS
BLACK
G~EEN BLACK BROWN
500 MM F = ,0005
Some Commonly Used Si zes of Condensers
MMF. MF. FIRST DOT
10 .00001 Brown
5:) .00005 Green
100 .0001 Brown
250 .00025 Red
500 .0005 Green
1000 .001 Brown
3000 .003 Orange
000 .01 Brown
The tolerance rating corresponds to the color code, i.e.,
The voltage rating corresponds to the code multiplied
Blue - 600 volt rating.
SECOND DOT
Black
Black
Black
Green
Black
Black
Black
Black
red - 2%, green - 5%, etc.
by 100. Example: Orange
THIRD DOT
Black
Black
Brown
Brown
Brown
Red
Red
Orange
dot - 300 volt rating;
