18WuD2x

ladder network • lamp driver 397
ladder network A network consisting of several L
sections in cascade. See L SECTION, 1, 2, 3.
ladder-type attenuator An attenuator consisting
of a ladder network equipped with a switching
circuit for selecting the output at various sections.
Input
ladder-type attenuator
Output
LAFOT Coded weather broadcasts aired every six
hours by the U.S. Weather Bureau through marine
radiotelephone broadcasting stations for the
Great Lakes region.
lag In computations relating the phase of alternating-current
signals, the extent to which one
quantity follows another in time (e.g., the current
lags the voltage by 90 degrees in a pure inductive
reactance). Compare LEAD.
lagged-demand meter A meter with a built-in time
delay.
lagging current Current that follows voltage (in
time). Also see LAG.
lagging load A load in which current lags behind
voltage (i.e., an inductive load). Compare LEAD-
ING LOAD.
lag network A phase-shifting circuit containing
series-resistance and shunt-capacitance arms. It
produces a lagging phase shift. Compare LEAD
NETWORK.
lambda wave An electromagnetic disturbance that
travels along the surface of an object. An example
is the surface wave characteristic of lowfrequency
propagation.
lambert Symbol, L. The centimeter-gram-second
(cgs) unit of luminance, equal to the brightness of
an ideal diffusing surface that radiates or reflects
light at 1 lumen per square centimeter. The SI
(preferred) unit of luminance is the candela per
square meter (cd/m 2 ); 1 lambert equals 10 4
cd/m 2 . Also see CANDELA.
Lambert’s law of illumination The illumination
of a surface by a point light source is inversely
proportional to the square of the distance between
the surface and the source. If the surface
is not perpendicular to the rays, the illumination
is proportional to the cosine of the angle of incidence.
laminated armature An armature for a motor or
generator, made of stacked laminations.
laminated contact A switch contact consisting of
a number of laminations—each contacting a conducting
counterpart.
laminated core A core for a transformer, choke, relay,
or similar device, made of stacked laminations.
laminated disk A layered recording disk.
laminated pole A pole within a motor, generator,
relay, electromagnet, or similar device, made of
stacked laminations.
lamination 1. A relatively thin sheet of metal cut
to a required shape to be stacked with other similar
sheets to form a laminated core or pole. 2. A
relatively thin sheet of plastic that is bonded together
and heat-formed with other similar sheets
to produce a sheet or piece of desired thickness
and strength.
lamp A device for converting electrical energy into
visible light. The term includes a number of devices
(e.g., arc lamp, fluorescent tube, incandescent
lamp, mercury-vapor lamp, and neon
bulb).
lamp-bank resistor A makeshift heavy-duty resistor
consisting of several incandescent lamps
arranged so that they can be switched in various
series, parallel, and series-parallel combinations
to vary the resistance provided by the
filaments.
lampblack Carbon obtained from soot deposited
by a smoky flame. The substance is used as the
basic material for some resistors.
lamp cord A two-wire insulated cord, used with
low-wattage alternating-current appliances at
117 volts. The wire is usually stranded copper
equivalent to American Wire Gauge (AWG) #16.
lamp dimmer See DIMMER.
lamp driver A usually single-stage circuit for amplifying
a small pulse to drive an indicator lamp.