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E 1. Symbol for VOLTAGE. 2. Symbol for ELEC-
TRIC FIELD STRENGTH. 3. Abbreviation of
EMITTER. 4. Symbol for prefix EXA. 5. Symbol
for ENERGY.
e 1. Symbol for VOLTAGE. 2. Abbreviation of
EMITTER. 3. Symbol for ELECTRON CHARGE. 4.
Symbol for the natural logarithm base (approximately
equal to 2.71828). 5. Symbol for ECCEN-
TRICITY. 6. Abbreviation of ERG.
EAM Abbreviation of electronic accounting machine.
E and M terminals The output and input leads in
some signaling systems. Also called E and M
leads.
early early sound Sound propagated through
solids and/or liquids that reaches a pickup device
(such as a microphone) before the sound
propagated through the air. In general, sound
waves travel faster as the medium becomes more
dense.
early-failure period The period immediately after
manufacture of a device, during which the failure
rate (caused by defects in equipment or workmanship)
is high.
early-warning radar Abbreviation, EWR. A radar
system that produces immediate warning when
enemy aircraft enter the monitored area.
earphone 1. Headphone (usually a single unit).
2. Telephone receiver. 3. A miniature acoustic
transducer that is small enough to be inserted
into the ear.
earpiece See EARPHONE, 3.
earth 1. The ground. 2. An electrical connection to
the earth (see GROUND CONNECTION, 2). 3. In
space communications, the planet Earth.
earth connection See GROUND CONNECTION, 2.
earth currents 1. Electric currents induced in the
earth by current flowing through underground or
underwater cables. 2. Electric currents flowing
through the earth between ground connections of
electrical equipment.
earth ground 1. A common connection to an electrode
buried in the earth so that good conductivity
is maintained between the common circuit
point and the earth itself. 2. A rod driven into the
surface of the earth for use as a common circuit
connection.
earth inductor A magnetometer consisting of a
coil that is rotated in the earth’s magnetic field. It
delivers an alternating-current (ac) voltage proportional
to the field strength. Also called generating
magnetometer.
earth-moon-earth See MOONBOUNCE.
earth resonance A resonant effect at extremely low
frequencies, caused by reflection of currents
within the earth. Resonant currents have been
tested as a means of communicating with submarines
worldwide.
earth’s magnetic field Also called geomagnetic
field. The natural magnetic field whose lines of flux
extend from north to south. The earth’s magnetic
poles, also called the geomagnetic poles, do not exactly
coincide with the geographic poles. The field
somewhat resembles that of a bar magnet.
Eastern Standard Time Abbreviation, EST. Local
mean time at the 75th meridian west of Greenwich.
east-west effect The phenomenon in which the
number of cosmic rays approaching earth near
the equator from the west is greater than that
from the east by 10 percent.
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