Faraday shield
an electrostatic (E field)
shield made up of a conductive or partially
conductive material or grid. A Faraday cage
or screen room is effective for protecting in-
side equipment from outside radiated RF en-
ergies.
Faraday’s law
one of Maxwell’s equa-
tions that describes the fundamental relation-
ship between induced voltage and a time-
varying magnetic field.
For a conducting
coil, the induced voltage is proportional to the
time rate of change in the magnetic flux link-
ing the coil. This change may be produced
either by actual variation of field strength or
by relative motion between coil and field. See
also
Maxwell’s equations
.
Faraday, Michael
(1791–1867) Born:
Newington, Surrey, England
Faraday is best known as the greatest ex-
perimental physicist of the 19th century. It
was Faraday who invented the electric mo-
tor, generator, and transformer, and first de-
scribed electromagnetic induction and the
laws of electrolysis.
Faraday had no for-
mal schooling, although he attended many
lectures. The most inspirational of these lec-
tures were by the famed chemist Sir Humphry
Davy. Faraday became Davy’s assistant and
thus began an extraordinary career as an ex-
perimentalist.
Faraday’s contributions are
recognized by the use of his name as the unit
of electrical capacitance, the farad in the SI
system, and the Faraday constant in electrol-
ysis.
farm
See
processor farm
.
fast Fourier transform (FFT)
a compu-
tational technique that reduces the number
of mathematical operations in the evaluation
of the discrete Fourier transform (DFT) to
N log
2
N.
fast neutrons
neutrons emitted from
fission reactions which travel at velocities
higher than the average velocity of atoms un-
der random thermal motion.
fast packet networks
networks in which
packets are transferred by switching at the
frame layer rather than the packet layer. Such
networks are sometimes called frame relay
networks. Current thinking views frame re-
lay as a service, rather than transmission,
technology.
fast reactor
a reactor which maintains a
critical chain reaction with fast neutrons and
which does not require a moderator.
father wavelet
the scaling function in the
coarsest resolution in wavelet analysis.
fault
(1) in hardware, a physical defect
or imperfection of hardware. Typical circuit
faults are shorts opens in conductor, defects
in silicon, etc. See also
disturbance
.
(2) in software, the manifestation of an
error.
fault avoidance
a technique used to pre-
vent or limit fault occurrence (for example,
with signal shielding, fan-out limitation, and
power dissipation decrease).
fault confinement
technique that limits
the spread of fault effects to some area of
the system and prevents propagation of these
effects to other areas.
fault coverage
the measure of test qual-
ity expressed as the percentage of detected
faults.
fault detection
the process of locating dis-
tortions or other deviations from the ideal,
typically during the process of automated vi-
sual inspection, e.g., in products undergoing
manufacture.
fault indicator
a small indicating unit
equipped with a permanent magnet and piv-
oting pointer which is hung on a transmission
line suffering intermittent faults of unknown
origin. After a fault occurs, fault indicators
are inspected. Each shows the presence and
c
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