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24 AMI • Amperian whirl
Character Symbol Character Symbol
A . — U . . —
B — . . . V . . . —
C . . . W . ——
D — . . X . — . .
E . Y . . . .
F . — . Z . . . .
G ——. 1 .——.
H . . . . 2 . . — . .
I . . 3 . . . — .
J — . — . 4 . . . . —
K — . — 5 ———
L —— 6 . . . . . .
M —— 7 ——. .
N — . 8 — . . . .
O . . 9 — . . —
P . . . . . 0 ——
Q . . — . period . . ——. .
R . . . comma . — . —
S . . . question — . . — .
T — mark
American Wire Gauge (AWG) Diameters
AWG Millimeters Inches
1 7.35 0.289
2 6.54 0.257
3 5.83 0.230
4 5.19 0.204
5 4.62 0.182
6 4.12 0.163
7 3.67 0.144
8 3.26 0.128
9 2.91 0.115
10 2.59 0.102
11 2.31 0.0909
12 2.05 0.0807
13 1.83 0.0720
14 1.63 0.0642
15 1.45 0.0571
16 1.29 0.0508
17 1.15 0.0453
18 1.02 0.0402
19 0.912 0.0359
20 0.812 0.0320
AWG Millimeters Inches
21 0.723 0.0285
22 0.644 0.0254
23 0.573 0.0226
24 0.511 0.0201
25 0.455 0.0179
26 0.405 0.0159
27 0.361 0.0142
28 0.321 0.0126
29 0.286 0.0113
30 0.255 0.0100
31 0.227 0.00894
32 0.202 0.00795
33 0.180 0.00709
34 0.160 0.00630
35 0.143 0.00563
36 0.127 0.00500
37 0.113 0.00445
38 0.101 0.00398
39 0.090 0.00354
40 0.080 0.00315
AMI See ALTERNATE-MARK INVERSION SIGNAL.
A-minus Also, A-. The negative terminal of an A
battery, or pertaining to the part of a circuit connected
to that terminal.
ammeter An instrument used to measure the
amount of current (in amperes) flowing in a circuit.
ammeter shunt A resistor connected in parallel with
an ammeter to increase its current range. Also see
AYRTON-MATHER GALVANOMETER SHUNT.
ammeter-voltmeter method The determination of
resistance or power values from the measurement
of voltage (E) and current (I). For resistance,
R = E/I; for power, P = EI.
ammonium chloride Formula, NH 4 Cl. The electrolyte
in the carbon-zinc type of primary cell.
Also called SAL AMMONIAC.
AMNL Abbreviation of AMPLITUDE-MODULATION
NOISE LEVEL.
amortisseur winding 1. A winding that acts
against pulsation of the magnetic field in an electric
motor. 2. A winding that acts to prevent oscillation
in a synchronous motor.
amorphous substance A noncrystalline material.
amp 1. Slang for AMPERE. 2. Slang for AMPLIFIER—
especially in audio high-fidelity applications.
ampacity Current-carrying capacity expressed in
amperes.
amperage The strength of an electric current (i.e.,
the number of amperes).
ampere (Andre Marie Ampere, 1775-1836). Abbreviations,
A (preferred), a, amp. The SI base unit of
current intensity (I). The ampere is the constant
current that, if maintained in two straight parallel
conductors of infinite length and of negligible circular
cross section and placed 1 meter apart in a
vacuum, would produce between the conductors a
force of 2 × 10 –7 newton per meter. One ampere
flows through a 1-ohm resistance when a potential
of 1 volt is applied; thus I = E/R. Also see MI-
CROAMPERE, MILLIAMPERE, NANOAMPERE,
and PICOAMPERE.
ampere balance A device consisting of two conductors
in which the force between them (caused
by current) is balanced against the gravitational
force exerted on an object in the gravitational
field of the earth. Used for the precise determination
of current of large dimension, or of the size of
the ampere.
ampere-hour Abbreviations: Ah, amp-hr. The
quantity of electricity that passes through a circuit
in one hour when the rate of flow is one ampere.
Also see BATTERY CAPACITY.
ampere-hour meter An instrument for measuring
ampere-hours. It contains a small motor driven by
the current being measured and which moves a
point on an ampere-hour scale. The motor speed is
proportional to the current. The position of the
pointer is proportional to current and elapsed time.
Ampere’s law Current flowing in a wire generates
a magnetic flux that encircles the wire in the
clockwise direction when the current is moving
away from the observer.
ampere-turn Symbol, NI. A unit of magnetomotive
force equal to 1 ampere flowing in a single-turn
coil. The ampere-turns value for any coil is obtained
by multiplying the current (in amperes) by
the number of turns in the coil.
Amperian whirl The stream of electrons in a
single-turn, current-conducting wire loop acting
as an elementary electromagnet.