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E L E C T R I C A L
P R I N C I P L E S
7 1
A B C O
First s i g n i f i c a n t d i g i t
Number ot z e r o s
@
R e s i s t o r
C o l o r
C o d i n g ( V a l u e s I n ohms)
T h i r d sipniticont d i g i t
V o l t o g e ~ e s t '
Tolerance
DecimOI Multiplier
@
C o p o c i t o r
Color
Coding (Volues in micro-microtorods)
Black
Brown
Red
Orange
Yellur
Crwn
Multiplier
Tolerance
0
1
2
3
4
5
0
1
2
3
4
S
Black
Brown
Red
Orannc
Yellow
Creen
Rlack
Bmwn
Red
Orange
Yellow
Green
-
1 0
1 0 0
1 . 0 0 0
1 0 . 0 0 0
1 0 0 . 0 0 0
not
Color
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
<;ray
White
Cold
Silver
N o
Color
Blur
Gray
G m c i t a n c e
in
micromicrofarads
(uuL)
None
Silver
Cold
f 20%
t
10%
t 5%
6
7
8
9
Figure 66. Color Coding Used on Carbon Resistors and Mica Capacitors
Signiricant
Figures
A
R
C
Blsck
Brown
Red
Orsnac
Yellow
C m n
Blue
Violet
k ? Z e
Cold
Silver
No Color
Blue
Violet
(;my
White
will signify a 40 mmfd capacity accurate within
the anode circuit since ,the grid is at -25 volts.
A 2
7 C
and tested for operation up to 5 00 volts.
With no current flowing through the load resistor
R there will be no potential drop across it, and
I . O O O . 0 0 0
1 0 . 0 0 0 . 0 0 0
-
-
Dccimol
Multnplier
D
BASIC CIRCUITS
point A will be at the same poten.tia1 as the battery
+
terminal, i.e., +I50 volts.
In Figure 67B the
Before proceeding with the actual electronic cir-
switch
S
has been transferred over to the cathode,
cuits, several elementary principles will be reviewed
and several basic circuits which will facilitate later
cxplana~tions will be discussed.
In all the electronic circuits, voltages are referred
to the cathode. The cathode will thus
be
at zero
voltage and all voltages positive with respect ro the
cathode will be considered above the cathode and
will be indicated with a plus sign (+). All volt-
ages negative with respect to the cathode will be
considered
below
the zero voltage of the cathode
Csparitivr
Tolerance
E
thus placing the grid at carhode potential.
Con-
duction will take place through the tube and
through the load resistor
R.
Assume that 10 milli-
amperes of currenr pass through the tube.
With
the given value of 10,000 ohms for the load resis-
tor, the potential drop across R will be 100 volts.
The direction indicated is the direction of electron
flow in conformity wirh the direction of flow
through the tube. The potential drop across the
tube will be E
=
Ea
-
I R
=
150
-
100
=
5OV,
and will be indicated with a minus sign (-).
For
since the sum of the potential drops across the
example, in the simple triode circuit of Figure 67A,
series components of a circuit must equal the po-
the grid is at -25 volts and the anode is
a t
+I50
tential of the source. The potential at the midpoint
volts.
tap
M
in Figure 67A is +I50 volts before con-
In Figure 67A it is assumed that the triode will
duction starts.
However, when sthe tube is con-
cut off at -1 5 volts; therefore, no current flows in
ducting, the potential at point
M
is + l o 0 volts.
-
DC
Test
Voltnge
F
Dot
Color
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